WARNING: This page is about a different car, the 2003 Pontiac Sunfire and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
Remove the screws (2) from the rear door lower sealing strip.
Remove the rear door lower sealing strip (1) from the quarter panel.
Fig 1: Removing Rear Door Lower Sealing Strip From Quarter Panel