Any one knows where the wire to the spot light on a chevy 1/2 ton be connected to and what size fuse and voltage reducer should I use, since the light is 6volts but I am running 12 volts?

Anyone has the instructions for truck (manual Transmission) back-up light switch wiring. I know the switch mounts below on the transmission stick and one wire goes to the light in the back but how about the other wire?