simple.....once you have cut and stripped the rca leads.....red white yellow black plug ends your should be left 8 wires.....the harness plug from the back of the stereo with the green/green and black...purple/purple and black white/white and black grey/grey and black wiring is the one you need to solder the ends of the rca leads to...ie green to green, bare wire to green and black and so on..
if your really stuck i ll be happy to sort it