WARNING: This page is about a different car, the 2010 Porsche Cayenne, 2009 Porsche Cayenne, and 2008 Porsche Cayenne. However, it is still accessible from the selected car via links, so may be relevant.
Carefully insert a plastic spatula at the four points between the air vent and dashboard and prise out the air vent.
Fig 1: Inserting Plastic Spatula Between Air Vent And Dashboard
Courtesy of PORSCHE CARS NORTH AMERICA, INC.
Press the electrical plug connection and pull off the plug.