To place mesh ribbon in a Christmas tree, you'll need to first measure the length of the ribbon needed to go around the tree. Then, cut the ribbon to the right length. Next, starting at the bottom of the tree, loop the ribbon around the tree, tucking the ends in as you go. You can also twist the ribbon in different directions to create a more interesting look. Once you've reached the top of the tree, secure the ribbon with a piece of tape or a hook. Finally, add ornaments and other decorations to complete the look.