WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
Remove the screws from the inboard/outboard rear seat back hinge covers.
Fig 1: Identifying Seat Belt Side Buckle & Retaining Nut