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.
Install the air deflector to the fascia.
Install the push-pin that retains the air deflector to the fascia.
Install and fully seat the tabs that retain the air deflector to the fascia.