Now that the PC is fully built it is time to test it and see if it works. Make sure all of the wires are pluged into where they need to be so that that won't be an issue. Now take a power cord and plug it into the power supply on the back. Once you have done that make sure the switch on the power supply is flipped to on and press the power button on the front/top of the PC. If everything was wired correctly the PC should turn on!
Once the PC is booted up press the delete key to bring up the BIOS screen. Here you can choose which drive to boot off of, check to see if the memory is running correctly, and other things that are a little too complicated for this tutorial.
The FINAL step is to install an opperating system on it. Most people if they are building their own PC will choose to instal windows but there are other options like linux.