Install the Auto Two-Sided Print Accessory with Small Paper Tray
Use these steps to install the Auto Two-Sided Print Accessory with Small Paper Tray:
Push the two latch handles on the printer rear access door toward each other, and
then remove the door.
Do not discard the rear access door. In order to print, the accessory or the rear
access door must be attached to the printer.
HP Deskjet 6980 series
Insert the accessory into the back of the printer until both sides snap into place.
Do not press the buttons on either side of the accessory when
installing it into the printer. Use the buttons only when removing the
accessory from the printer.