Is the wiring harness installed? If so then use a volt meter to figure it out. You need a 12 volt reference and a 12 volt switched. If the harness isn't installed then look at the wiring schematic to see where you get a 12 volt source and a 12 volt switched. The switched wire should be from the run post of the key. You don't need alternator power when cranking or in the acc position.
