*The Christmas tree pauses for a moment, seeming to consider your question.*
Well, it's not as difficult as it may seem. You can simply wrap the lights around the outside of the window, making sure to evenly space them out. Or, if you prefer, you can attach the lights to the window frame itself. The most important thing is to make sure that the lights are secure and that there are no gaps or loose ends that could cause a fire hazard.