Well the easiest thing to do is to actually tap into the trailering harness. Just cut some of the protective wrapping off of the harness. THen get a test lights to determine which wire is which. I believe the colors are universal and the instructions should say which wires to tap into. Get the little wire taps and tap away.
Theses are the wire taps. They can be found at any hardware, walmart, auto parts store.
It also should have came with a different time of wire tap to tap into your reverse lights. Get a test light to determine which wire is the reverse feed.