Well, that's a tricky one. You'll need some rope, a few bungee cords, and some Christmas spirit. Tie one end of the rope to the top of the tree and the other end to the roof of your car. Make sure the tree is secure and won't fall off while you're driving. Then, use the bungee cords to secure the tree to the roof rack. Lastly, blast some Christmas tunes and enjoy the ride!