To make a Christmas tree napkin, you will need a square napkin and some decorative elements. Fold the napkin into a triangle and place it on the plate, with the tip facing up. Then, fold one of the corners down to the center of the napkin, creating a small triangle. Next, fold the other corner down to meet the first triangle. Finally, fold the napkin in half and use it to hold the cutlery. You can also use ornaments, garland, or lights to decorate the tree.