WARNING: This page is about a different car, the 2007 Chevrolet Monte Carlo and 2007 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
Align the DLC to the I/P trim pad.
Fig 1: View Of Data Link Connector (DLC)
Courtesy of GENERAL MOTORS CORP.
Slide the DLC upward in order to engage the tab (1).