Now you need to install the motherboard into the case. If you’re following this tutorial, the CPU, fan and memory will already be installed onto the motherboard, so you will be installing this whole setup into the case now.

1. Turn your PC case onto its side and move all the power leads from the power supply out of the way so that you have clear access to the motherboard plate. If you are using a case in which the motherboard mounting plate can be removed, you may wish to remove it now and install the motherboard outside of the case itself.
2. Locate the holes on the motherboard and the holes on the case or motherboard mounting plate. You might want to hold the board just above the case motherboard plate and see which holes on the case line up with holes on the motherboard. All motherboards have mounting holes in different places.
3. Now gather your standoffs. Screw them into the holes in the case or mounting plate that line up with holes on the motherboard. You can tighten them with a 3/16″ nut driver or by hand. Some cases have small spacers that snap into place. With these, you push them through the mounting plate from the back side and they will snap into place.
4. For the holes on the motherboard that line up with an eyelet hole on the case (a hole that is very long so that you can slide things in it), install a plastic stand-off on the motherboard. The stand-offs should poke through the motherboard and expand to keep them in place. The little disk on the other end of the stand-off will later be used to slide into the eyelet holes. If your case does not provide eyelet holes, do not worry about this step. Most cases use only the metal standoff screws to hold the motherboard, which is a hell of a lot easier than the slide-in variety.
5. Take the motherboard by its edges and hold it over the case. Align it so that it is properly aligned with the rear connectors facing backward, etc.
6. Lower the motherboard into the case. Sit it on top of the standoffs you just installed so that each standoff lines up with a screwhole on the motherboard. If you happen to be using any of the slide-in standoffs, you will need to slide these into their eyelet holes as you lower the board into the case.
7. Inspect the screws you will use to tighten the board down. If the head of the screws are too wide, and you think they might contact any circuitry on the motherboard, place a plastic washer over each hole. I’ve had some ATX boards refuse to start up later because they were grounded somewhere to the case, probably by a screw.
8. Tighten the board down. Install the screws into each of the standoffs underneath, through the board and the washers if you used them. Tighten them down by hand first, then finish them with a screwdriver. Make sure you do not tighten them too much. You don’t want to crack your board. Just make them snug so that the board doesn’t wiggle around in the case. It may be necessary to adjust the position of the board somewhat in order to get the holes aligned enough with the standoffs to tighten down the screws.
9. If you were installing the board to a removable mounting plate, install the motherboard mounting plate back into the case. On some cases, the plate is installed from the side. On these, you insert the bottom edge of the plate into a guide rail on the bottom of the case and then rotate upward. The top edge of the plate will contact the case, at which point you can screw it in or a spring loaded handle will lock it in. On other cases, the plate may slide in a different way, from the rear for example. These plates are then easily removed later if you ever need to remove the motherboard.
10. Double check your work. Check to be sure that the back of the motherboard is not touching any part of the case or mounting plate. Make sure the slots and connectors line up with the holes on the back of the case. And definitely be sure that the board is rigid and tight. If you press down on the board at any point, it should not bend down.