Installing LED tailgate light. Pacer performance

Hey, I have a 2004 silverado 1500 and am installing a Pacer performance LED tailgate light. Has anyone done this? It says to connect the "constant" wire to the vehicle constant wire. I just cant find this wire. Does anybody Know where it is? Or I could use a wiring diagram, I just cant find one.

A Haynes manual should have a wiring diagram.

Thanks, I found the Haynes manual. I think I'll give it a try.