smokinmaxima03

Ok just wondering if anybody can help me out on installing an AMP to my stock head unit. My ride is a 03 Maxima SE. I hooked up everything already, I think, but it seems like I can't find the Power off wire for the AMP to connect to, so power is on constant just for now until I find the right wire to connect it to. Also when I turn up the volume somtimes the music cuts off kinda like a skipped CD. Also when I turn on my headlights the Light on the OEM head unit screen goes blank. Please HELP!!!! THANKS in advance!!!!!