Glad you asked...
A fuel gauge works off of a 12 volt power and the float on the fuel tank that puts resistance on the ground to the gauge. To wire you will run a 12 volt power supply from the fuse box to the positive wire on the gauge. And you will need to run a wire from the float in the tank to the negative lead on the gauge.
Then again, this answer might help you...
To wire a fuel gauge, you should only have a single wire coming from the fuel tank. Use this wire to the input of the fuel gauge. The gauge itself should have a ground and a power wire to allow it to function.

