Rep Power: 0

I have used APC Guage Indiglo faces, the are just the 3 guages, and two wires from each are stripped. I tested the guage from a seperate battery source and they light up. My problem is how do I hook them up to my headlights. Obvisouly I want them to turn on when I have the lights on @ night. Where on earth is the Headlight circuit that I need to tap into. How do I do this, please help, i'm confused. I understand that one wire is power and the other is ground/negative, I think!

REALLY Confused but would appreciate the help.

[N]ex[G]en