http://www.r1200gs.info/howto/relay.htmlIts a motorcycle article, but its relative. 12v, etc, etc.
Good luck, remember to keep the magic smoke in your lights, wiring, relay and switches. If the smoke gets out, get new parts and keep a fire extinguisher handy.
Wire it all up, and connect your negative side up to the battery first, then connect the positive side.
You can get all your stuff from:
MRO Electronics, #5, 1247 36 Ave NE, 403-291-0501
B&E Electronics, 444 Manitou Rd. S.E (Across Blackfoot from National4WD, off Manhattan Road)