Make sure you turn off the power, unplug the power cord, and check that all wiring has been disconnected. The cord may be damaged, resulting in electric shock or fire.
Electrostatic discharge can damage printer parts. Make sure you discharge static electricity from your body by touching grounding yourself before installing the ethernet board.
Turn off the printer by pressing the 
button.
Disconnect all cables such as the power cord and USB cable.
Loosen the two screws and then remove the cover.
Install the ethernet board straight into the additional interface slot for the ethernet board.
Insert the ethernet board firmly into the slot.
Do not remove the cover of the ethernet board.
Do not touch the terminals of the ethernet board.
Secure the ethernet board with the two screws.
Connect the removed power cord and USB cable.
Press the 
button, select the Job/Status > Options, and then confirm if the ethernet board is installed correctly.
Select Settings > General Settings > System Administration > Firmware Update > Update to update the firmware.