IBM X.25 - Manual (Page 20)

11. Install the adapter by holding it by the top and firmly pressing it
into the expansion slot.
12. Align the slot in the card-retaining bracket with the hole in the
rear panel of the system unit.
13. Insert and tighten the screw to secure the card-retaining bracket
to the rear panel of the system unit.
14. If you have other adapters (or options) to install, do so now.
Refer to the Operating and Installation documentation provided
with your computer system if more information is required for
other adapters or options.
15. Replace the system-unit cover.
16. Reconnect all cables previously removed from the system unit.
17. Plug all power cords into electrical outlets.
2-4 X.25 Co-Processor PCI GTO