The horn came with a relay and when I bought it they had some deal where they threw in a "deluxe" wiring kit.
It wires up pretty easy..old horn wires to relay and then relay wires to new power from batt etc etc.
theres quite a few posts around here of different wire installs, it's been so long I'd have to look at where I wired mine into to be sure exactly how I did it. I'm pretty sure I just spliced into the harness under the seat to get the horn wire signal to the relay and then ran the wires out to the horn along the harness by the frame under the tank. Then power the relay from the batt term.
For the loud sound it's worth an afternoon of tinkering to get it installed.
heres a good thread with pics and links about horns and installs...
http://www.bonnevilleamerica.com/forums/...part=1&vc=1
