Yes, I'm here to help with that! To change a fuse in Christmas lights, start by unplugging the lights from the outlet. Then, locate the fuse box on the string of lights and use a small screwdriver to remove the fuse. Make sure you use a fuse that is the same amperage and voltage as the one that came with the lights. Replace the old fuse with the new one, and then plug the lights back in. Remember to always use caution when working with electrical components.