Dell D31M Owner's Manual page 106

Steps
1. To remove the PCIe dummy bracket, insert a flat-head screwdriver in the hole of the bracket, push the bracket to release it,
and then lift the bracket out of the system.
2. Lift the pull tab to open the PCIe door.
3. Insert the optional SMA module into its slot on the system board.
4. Route the SMA module cable through the cable holder on the chassis.
5. Close the cable holder to secure the SMA module cable in place.
Next steps
1. Install the wireless card.
2. Install the side cover.
3. Follow the procedure in
106 Removing and installing Field Replaceable Units (FRUs)
after working inside your computer.