Where do you find the fuse that controls the gas gauge on your car?

Obtain a Haynes or Chilton manual for the make, model, and year of your car. The answer will probably be in there. Assuming that the gas gauge has a fuse...I don't know if they do or not. The manual would likely have troubleshooting steps to resolve whatever problem you're having with your gas gauge. You might find such a manual at the library. Otherwise, you can buy one at a parts store, or on amazon.com, or eBay.