As I understand it, hold the arm up in place with it pointed forward, and screw the top cap down until it's tight against the bracket mounted to the car body. It's a bit tricky because you are fighting against a spring. Then confirm that the arm swings fully in both directions. As it swings, it's screwing in and out a little bit, but that's by design. You just need to be sure it doesn't bind at either extreme of it's swing. Also check for play. Oh, and grease it up real well before hand.
By the way, this only applies to 230's. The later cars have a different setup.
