WARNING: This page is about a different car, the 2003 Oldsmobile Bravada, 2003 GMC Envoy XL, 2003 GMC Envoy, and 2003 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
Position the scuff plate to the rocker panel.
Apply downward pressure on the scuff plate to seat the retaining tabs.
Install the push-pin that retains the scuff plate to the rocker panel.
Close the rear door.
Fig 1: Positioning Scuff Plate To Rocker Panel - Rear