To decorate a window with lights, begin by selecting lights that complement the existing decor, such as string lights, fairy lights, or icicle lights. To make a visually appealing display, combine lights with garlands or greenery. Consider using suction cups or hooks to hang the lights directly on the window, or drape the lights across the top of the window with a curtain rod. Finally, when using electrical decorations, use the lights to create a warm and inviting ambiance while also taking proper safety precautions.