To curl Christmas tree ribbon, you can follow these steps: 1. Get a piece of ribbon that is long enough to fit around your Christmas tree. 2. Cut the ribbon into long strips, about 1-2 feet long. 3. Take one of the strips and twist it around your finger, making a spiral. 4. Place the spiral on the Christmas tree and secure it in place with a pin or a piece of tape. 5. Repeat this process for the entire tree, working from the top down. You can also experiment with different colors and patterns of ribbon for a more festive look.