Yep, it goes to the horn. this is the ground side of the horn circuit. I'm not sure what you are using for a wireing harness but the hot wire comes from any circuit that is hot all the time. You can run it through a horn relay if you want. I didn't, its just wired up to the horn circuit on my fuse box. I rewired my truck with a Painless harness.

Hope this helps
George