Most likely you have a high level input on your amp. One option is just to splice of your rear speakers and run it to this speaker level in put. if you don't have speaker level inputs then your going to have to get you a converter that turns your speaker inputs to RCA outputs sorry brainfort can't remeber what one of those is called other than that all you should need is a fused 8 or 4 gauge input depending on the size of your amp, fuse, ground and switch other wise your amp is going to always be on. One option here is finding out what the color scheme of the wires is under your dash and running a relay from your auxilary turn on so the amp would only come on when you turn yur ignition on. This is a little complicated but if you don't wanna touch your head maybe the best way. Hope this helped peace
Owners Manual! read it and find out what wire does what! or you could just start cutting untill your car don't work no more! But there is a wire tester, easiest way to do it w/o wasting your time!