They come on automatically when you shift to reverse, I did not wire them to a switch but its possible, there are some wiring diagrams on this forum that show how to do it. I just wanted them to come on without me having to do anything special.
I wired them to the the reverse and ground poles on the 7-way trailer harness. There is a wiring diagram on the cover of the 7-way connector that will show you which pole to connect to.
The harness is mounted by 2 bolts and connected to the electrical system by 2 connectors that easily disconnect. I removed the harness and place it on the workbench. I opened up the wiring cover and traced the wires to a convenient location to splice into and soldered in the wire leads I needed. I re-wrap the protective cover over the wires. On the other ends of the 2 leads I crimped on male blade connectors. Then I re-installed the harness in the vehicle. Now I had a pigtail ready to connect to when I installed the lights.
you can see most of the work and the wiring diagram on the cover in the picture. I was very careful to seal up and insulate all the connection. All in all it was very easy.
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