To use ribbon on a Christmas tree, you will need to first gather some ribbon in the color of your choice. Then, you will want to tie one end of the ribbon around the top of the tree and start wrapping it around the tree, making sure to leave enough ribbon at the end to tie another knot. Once you have wrapped the ribbon around the tree, tie the second knot to secure it in place. Now you have a festive and beautiful Christmas tree, adorned with ribbon.