To make a Christmas tree napkin, you will need some green paper or a green cloth napkin. Start by folding the napkin in half lengthwise and then fold it in half again to create a square. Next, take one corner of the square and fold it up to meet the top edge of the napkin. Keep folding the corner until it reaches the center of the napkin, creating a triangle shape. Flip the napkin over and repeat this process with the other corner. When both corners are folded, you should have a diamond shape.