Go to your local Cat dealer or order on -line from somebody the wiring harness for this job, it's only a few bucks and a lot less screwing around than wiring to the battery. One end is a double prong harness which plugs into the wiring of the sled, usually under the handlebar cover, the other end is the RCA female plug with a ribbed case. Drill a hole in the cover by the key or wherever and just jam the RCA plug into it and the ribbing will hold it in place.
If you don't want the wire hanging off your helmit and flailing around while you drive, some guys run it thru their jackets and out the sleeve, in that case just plug the harness in and let the RCA plug part come out the handlebar someplace. Just remember it is plaugged in before exiting the machine or you'll rip the cords out.