To hang Christmas lights in windows, you'll need a few things: Christmas lights, hooks or nails, and a ladder. First, decide where you want to place the lights and measure the length of the windows. Then, install the hooks or nails along the top and bottom of each window. Make sure they are spaced evenly apart. Once the hooks are in place, hang the lights along the hooks, starting at the top and working your way down. Finally, plug in the lights and enjoy your festive windows!