CITROEN DS4 Owner's Handbook Manual page 152

Front armrest
Comfort and storage device for the driver and front passenger.
The length of the armrest cover can be adjusted.
Longitudinal adjustment
 To move forwards, raise the lever.
The armrest slides forwards to its stop.
 To stow it, slide it fully back and press
down to lock it.
Storage
The armrest's compartment can hold up to
6 CDs.
 Raise the cover fully.