2005 Grand Cherokee aftermarket radio

Alright, I have a 2005 grand Cherokee with no amp(I think), and I'm trying to pur in an aftermarket radio. I bought the Pac c2r-chy4 interface, I believe I hooked it up right, but obviously I didn't because once I plug it in my jeep dies. If I try without the interface connected, the radio does nothing. I've been trying for hours, I just have no idea what else to do.