Ah, changing a fuse in Christmas tree lights! It's a fairly straightforward process. First, make sure the tree is unplugged and the lights are turned off. Then, locate the fuse box on the back of the tree. It should be marked with the wattage or voltage of the lights. Simply remove the old fuse and replace it with a new one of the same rating. Remember to always use a fuse with a higher rating than the lights require. Lastly, plug the tree back in and test the lights to make sure everything works correctly. Happy holidays!