WARNING: This page is about a different car, the 2003 Pontiac Montana, 2003 Oldsmobile Silhouette, and 2003 Chevrolet Venture. However, it is still accessible from the selected car via links, so may be relevant.
Open the liftgate
Remove the sill plate by pulling it from the floor of the vehicle
Fig 1: Removing Sill Plate From Vehicle Floor (Lift Gate)