The process of putting Christmas lights on a tree is a fairly simple task that can be accomplished with a bit of care and attention. Before starting, be sure to take the time to carefully inspect the lights to make sure there are no frayed wires or broken bulbs. Once the lights are confirmed to be in good working order, begin by determining how many strands of lights are needed to cover the entire tree. If the tree is tall, you may need to use an extension cord to reach the top branches.