WARNING: This page is about a different car, the 2002 Pontiac Montana, 2002 Oldsmobile Silhouette, and 2002 Chevrolet Venture. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Roof Auxiliary Air Outlets
Courtesy of GENERAL MOTORS CORP.
Align the roof auxiliary air outlets to the holes in the headliner.
Press the roof auxiliary air outlets into the headliner, locking in the retainers.