Okay, so first you'll need to gather some shells of different sizes and shapes. You can find these at the beach, or you can buy them at a craft store. Then, you'll need some hot glue and some wire. Once you have your supplies, you can start arranging the shells in a triangular pattern on the wire, starting with the largest shells at the bottom and working your way up to the smallest shells at the top. Once the tree is complete, you can decorate it with ribbons, lights, or whatever you like!