Trimming a Christmas tree is the process of adding ornaments and decorations to it. It's a tradition that has been around for centuries, and there are a few different ways to do it. Some people start by adding a tree topper, such as an angel or a star, and then adding a string of lights. After that, you can add ornaments, starting with the larger, more important ornaments and working your way down to the smaller ones. Finally, you can add tinsel or garlands for a more festive look. Whatever you do, make sure to take your time and enjoy the process!