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.
Fig 1: Installing Air Deflector To Fascia
Courtesy of GENERAL MOTORS CORP.
Install the air deflector to the fascia.
Install the push-pins that retain the air deflector to the fascia.
Install and fully seat the tabs that retain the air deflector to the fascia.