Verify that all parts are present.

Put brass locking button on spring.

Remove both tipping sleeve and lay chair on its back to expose the under side of the side frame.

Slide the spring with the brass nipple into the side frame until the nipple sticks out of the hole in the side frame.

Slide the anti tipper onto the side frame until it stops.  Depress the nipple and continue sliding the anti tipper on until the brass nipple locks it into position.