rhgore

I have a 1989 Mustang GT and I am having issues getting my 3rd brake light and license plate lights to work. I found out why they don't work. The wires are cut just inside the roof panel. I just purchased a wiring harness off of eBay for the hatch but I don't know how to hook it up. There are three clips and a ground wire on the harness. Where does it connect inside the car to the power source? Does it run all the way to the fuse box or does it connect somewhere else? Any help would be greatly appreciated.