To decorate an outdoor Christmas tree, start by placing it in a prominent spot in your yard, such as the front porch or a corner of your lawn. Then, use a string of lights to wrap around the tree, making sure to cover all sides and hiding any wires. Next, add a variety of ornaments, such as snowflakes, stars, and other holiday-themed decorations. Finally, top it off with a star or angel at the top. And voila, you have a beautifully decorated outdoor Christmas tree!