Tinsel is one of the most classic decorations for a Christmas tree. It's a long, thin, metallic or plastic material that is usually bright and shiny. To tinsel a Christmas tree, you'll need to start at the top of the tree and work your way down, hanging the tinsel on each branch. Be sure to use even spacing and make sure that the tinsel is secure on each branch. You can also add other decorations such as lights, ornaments, and garlands to make the tree even more festive.