WARNING: This page is about a different car, the 2003 Chevrolet Monte Carlo and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Front Seat Lumbar Knob
Courtesy of GENERAL MOTORS CORP.
Position the lumbar support knob to the lumbar shaft.
Install the lumbar support knob, pressing into place until fully seated