What you're actually doing when you build a PC

Building a PC means taking individual components — a processor, motherboard, memory, storage, power supply, and case — and connecting them together yourself. You are not soldering circuits or writing code. You are plugging parts into slots, screwing things down, and connecting cables. Most connections only fit one way, so you cannot easily break something by forcing it wrong.

The hardest part is usually not the assembly itself. It is deciding which parts to buy, making sure they work together, and then troubleshooting if the machine does not start on the first try. This guide walks you through the assembly steps in order. Before you start, you should have already chosen your parts — if you have not, go back to the "How to Build and Assemble Your Own PC" guide first.

Key Takeaways

  • Start by installing the power supply in the case, then the motherboard, then the CPU and RAM while the motherboard is still outside the case.
  • Ground yourself before touching components by touching a metal part of the case or wearing an anti-static wrist strap, because static electricity can damage parts.
  • RAM and the CPU cooler are the two places where you will feel real resistance — push hard enough that you hear a click, but stop if something feels wrong.
  • Do not plug in the power cable until you have installed the motherboard, CPU, RAM, and storage, and connected the power cables inside the case.
  • If the PC does not start, the most common causes are the power supply switch is off, the RAM is not fully seated, or the 24-pin motherboard power cable is not fully connected.

Prepare your workspace and protect against static electricity

Work on a non-carpeted surface if you can — a kitchen table or wooden desk is better than carpet. If you must work on carpet, touch a metal part of the case every few minutes to discharge static electricity. A better option is an anti-static wrist strap, which you can buy for $5 to $15 and clips to your wrist on one end and to a metal part of the case on the other. This keeps you at the same electrical potential as your components the whole time you work.

Lay out all your parts and tools before you start. You will need a Phillips head screwdriver (the one with a cross, not a flat blade). Have your motherboard manual nearby — you will need it to find where the power connectors go. Most motherboards come with a manual in the box, or you can read it from the manufacturer's website by searching for your motherboard model number plus "manual".

Install the power supply in the case

The power supply is a metal box that usually goes in the bottom rear corner of the case. Open the case by removing the side panels — usually two thumbscrews or latches on the back. Look inside and find the rectangular opening at the bottom or back where the power supply slides in.

Slide the power supply into the case with the fan facing down if there is a vent in the case bottom, or facing into the case if there is no vent. The power supply should sit flush against the case wall. Screw it down with four screws through the mounting holes on the back of the power supply into the case. Do not plug it in yet — the power switch should be off, and the power cable should not be connected.

Install the motherboard and I/O shield

The I/O shield is a thin metal plate that comes with your motherboard. It fits into the rectangular opening at the rear of the case and protects the ports on the back of the motherboard. Snap it in from the inside of the case first — it clicks into place.

The motherboard screws into brass standoffs that are already installed in the case, or that you may need to install yourself. Look at where the screw holes line up on your motherboard, and make sure there is a standoff under each hole. If not, screw a standoff into the case at that location. Then lower the motherboard into the case, line up the screw holes, and screw it down gently. Do not overtighten — snug is enough.

Install the CPU and RAM before closing the case

Install these two parts while the motherboard is still accessible and outside the case if possible, or while you have full access to it. Both are easier to install before the motherboard is fully seated.

For the CPU: Open the CPU socket by lifting the retention arm on the side. Line up the notches on the CPU with the notches in the socket — they only fit one way. Lower the CPU straight down into the socket without twisting or forcing it. Close the retention arm. If your CPU came with a cooler, install that now by following the instructions that came with it. Most coolers screw or clip to the motherboard around the CPU.

For RAM: Open the clips on both ends of the RAM slot. Line up the notch in the RAM stick with the key in the slot. Push down hard on both ends of the RAM until the clips snap closed and the RAM is flush with the slot. You should hear a click. If the RAM does not click in, it is not fully seated — push harder. If it still does not click after real pressure, check that the notch is lined up correctly.

Connect power cables inside the case

The power supply has several cables coming out of it. You need to connect the right cables to the right places on the motherboard and components. Use your motherboard manual to find the exact locations.

The 24-pin ATX power connector is the largest and goes to the main power socket on the motherboard, usually near the right edge. The 8-pin CPU power connector (sometimes 4-pin) goes near the CPU, usually in the top left corner of the motherboard. Both connectors only fit one way. Push them in firmly until they click.

If you have a graphics card, it may need a 6-pin or 8-pin power connector from the power supply. Connect that now. Connect SATA power cables to your storage drives — these are the flat, L-shaped connectors. Do not connect the power cable to the wall yet.

Install storage and connect data cables

Mount your storage drives in the case. SSDs usually go in a small slot on the motherboard itself — slide the SSD into the M.2 slot at an angle, then press down and screw it in. Larger 2.5-inch SSDs or 3.5-inch hard drives go in drive bays in the case and are screwed down.

Connect SATA data cables from the motherboard to each storage drive. These are thin, flat cables that plug into the drive on one end and into a SATA port on the motherboard on the other. Your motherboard usually has several SATA ports labeled SATA0, SATA1, and so on. Use the lowest-numbered ports first.

Power on and troubleshoot if needed

Before you plug in the power cable, do a final check: the CPU cooler is installed, the RAM is clicked in, the 24-pin and 8-pin power cables are connected to the motherboard, and the power supply switch is in the off position. Then plug the power cable into the wall and flip the power supply switch to on.

Press the power button on the case. The fans should spin, lights should come on, and you should hear the hard drive or SSD start up. If nothing happens, turn off the power supply when ready and check these things: Is the power supply switch on? Is the power cable plugged in? Are the 24-pin and 8-pin motherboard power cables fully seated? Is the RAM clicked all the way in? Try reseating the RAM by opening the clips, removing it, and pushing it back in hard until it clicks.

If the PC still does not start after checking those things, you may have a part that arrived damaged, or a connection that is not quite right. Do not force anything. Take a photo of your setup, write down what you have tried, and ask for help in a PC building forum or subreddit where people can see what you have done.

Frequently Asked Questions

Do I need an anti-static wrist strap?

Not absolutely, but it is cheap insurance. If you work on a non-carpeted surface and touch the metal case every few minutes, you are probably fine. If you work on carpet or move around a lot, a wrist strap is worth the $10 to avoid the small risk of frying a $300 part.

What if I install the RAM and it does not click?

Stop and check the notch. The RAM stick has a small notch cut into it, and the slot has a matching key. If they do not line up, you are pushing it into the wrong slot or the wrong direction. Remove it, rotate it if needed, and try again. When the notch lines up, push down hard on both ends until you hear a click.

Can I install the motherboard with the CPU and RAM already in it?

Yes, but it is harder because the CPU cooler and RAM take up space and make it difficult to maneuver the motherboard into the case. Most builders install the CPU, RAM, and cooler first, then lower the whole assembly into the case. Check your case and cooler size to see if there is room.

What should I do if the PC turns on but nothing appears on the monitor?

Make sure the monitor is plugged in and turned on, and that the video cable is connected to the graphics card (not the motherboard). If you do not have a graphics card, the video port should be on the motherboard itself. Reseat the RAM and the graphics card if you have one. If the PC still does not show a picture, the motherboard may need a BIOS update, which requires a different process.

Is it normal for the PC to be loud when it first starts?

Yes. All the fans spin up at full speed for a few seconds while the system checks itself. After that, the fans should slow down and the noise should drop. If the fans stay loud or get louder, the system may be overheating, which usually means the CPU cooler is not installed correctly or making good contact with the CPU.