WARNING: This page is about a different car, the 2006 Pontiac Montana SV6, 2006 Chevrolet Uplander, and 2006 Buick Terraza. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Engine Manifold Cover
Courtesy of GENERAL MOTORS CORP.
Align the cover to the studs on the engine, push down on the cover above the studs in order to engage the cover to the studs.