How do you decorate a pine tree in The Sims 2?

You can't decorate a pine tree in The Sims 2. You can, however, buy a tree that has already been decorated and place it in your Sims' property from the Buy Mode, or you can download Custom Content and install it to your The Sims 2 game, or place it in the Download folder under My Documents\EA Games\The Sims 2\, that has a decorated pine tree if you can find one.