The first step in fixing a broken Christmas light is to identify the issue. Is it the bulb itself that's broken, or is it the wiring or the socket? Once you know the problem, you can replace the part that's broken or fix the wiring. If it's the wiring, make sure to check all the connections to make sure they're secure and not damaged. If the socket is broken, you may need to replace it. Be sure to turn off the power before you begin any repairs.