If you want to sew a Christmas tree skirt, the first thing you'll need to do is find a pattern or tutorial that shows you how to make one. Once you have your pattern or tutorial, gather your materials. You'll need some fabric, thread, scissors, and a sewing machine or needle and thread. After you have all your materials, cut out the fabric according to the pattern or tutorial. Then, begin sewing the fabric together. Start with the top layer of the skirt and work your way down to the bottom layer.