A computer power supply is exactly what the name states. It will convert the AC current into the DC current that a computer needs. It will supply a very stable power going into your computer.
If you plan on running two video cards, more than three drives, or overclocking look at buying an aftermarket power supply with a capacity of 650W or more. If not, you should be completely fine with the power supply that came with your computer case. If you want something that is solid, get a 650W power supply or greater that has good reviews and you can't go wrong.
If you're not sure what wattage you need error to the side or bigger rather than smaller. A larger wattage power supply will run more efficiently, using less power, and will also supply a more stable power than a power supply that is working close to it's full potential. Recently I observed the results when swapping out a 450W power supply with a 650W power supply. The final consumption on my battery backup was actually about 20-30 watts less.
This used to be an area I was never concerned about, but lately, as we have devices that use more power, and require more stable power a cheap power supply can really be the crutch in an otherwise well built computer with high quality parts.
TIP! The best part of connecting the power supply is that all the connectors have different shapes, so if it fits, you have the right location.
There are four screws on the back of you computer case that hold the power supply in place. Just put the power supply in place and put the screws in.
TIP! Every connection on the motherboard needs to have power supplied to it. The picture below is incorrect.