WARNING: This page is about a different car, the 2003 Buick Regal and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
Slide the bezel onto the rear door handle.
Fig 1: Installing Bezel Onto Rear Door Handle
Courtesy of GENERAL MOTORS CORP.
Align the connecting clips on the bezel to the rear door trim panel.