I went to abc warehouse to get a radio installed now when I turn on my lightsit keeps blowing my fuse for the park lights, dash lights, and tail lights what did they do wrong?

 

I did somthing similar once while in Japan. I didn't have a schematic so I shot the wires with a meter. I found what I thought was a ground but it was actually the power for the radio back light. Of course everything worked fine untill I turned on the lights, then it popped the fuse. It was a easy fix, I just changed the ground wire over to a propper ground.