My general understanding of it is:
Output from the PC to 3.5mm... convert that to RCAs, and run that to your inputs on the amp/amps. From there, you get speaker wire, and run that to your speakers on the opposite side of the car that you used to run the power for the amp/pc.
Now, my only iffy part is on going from the PC to the Amp and keeping as high a sound quality as possible. PC generally outputs stereo 3.5mm... whereas amps input RCAs. There's a thread running right now discussing the best way of going about doing this: which audio cable option is better?
Here's a guide that helped me when I was learning about amps: http://www.crutchfieldadvisor.com/le...mplifiers.html
A picture of the connectors on a 4-channel amp: http://www.crutchfield.com/S-ZcHySwA...=XL#morephotos
On the right you have the power connections, in the middle you have the speaker wire connections, and on the left you have the inputs.