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The new lights are most likely grounded through the bumper, so you'll just have to find out which of the old wires is the power wire. If you have a volt meter you can put the black lead on the negative battery terminal, or any other good clean ground source, and the red lead on one wire at a time with the light switch on to find which one is power. Once you find out, just connect the power wire from the vehicle harness to the wire for the lights on the bumper.
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