Lights can be a challenge to fix on a Christmas tree, especially if they're tangled or have been damaged. Here are some steps to follow: 1) Unplug the lights from the wall outlet. 2) Untangle any knots or tangles in the string of lights. 3) Check the lights for any broken or burnt-out bulbs. 4) Replace any damaged bulbs with new ones. 5) Test the lights to make sure they're working properly before you put them back on the tree. 6) If the lights still don't work after following these steps, it may be time to get a new set