UPDATE via WEB GUI
1) Go to http://192.168.1.200/ or your specified IP address
2) Backup the current configuration by navigating to the "Other Settings" section in the main menu. Locate the "Config Operation" at the bottom of the page, press the "SAVE" button, and save the *.json file.
3) From the main menu, navigate to the "File Systems" section.
4) Select "Firmware" and click the "Upload file" button.
6) Upload the "mgb4-install_3.0.tgz" file.
6) Create the "mgb4-flash" flag file by pressing the corresponding button.
7) Optionally, create "mgb4-keep" flag file by pressing the corresponding button to keep the current configuration after update.
8) Reboot the FG4 MultiBox by pressing Reboot button.
9) The FG4 MultiBox boots into the flashing process.

UPDATE via SDCARD (keeping configuration is not possible)
1) Power off the FG4 MultiBox.
2) Copy the "mgb4-install_3.0.tgz" to the SDCARD.
3) Create the "mgb4-flash" file on the SDCARD. (blank txt file with no extension)
4) Insert the SDCARD into the FG4 MultiBox.
5) Power on the FG4 MultiBox.
6) The FG4 MultiBox boots into the flashing process.
7) The FG4 MultiBox powers off itself after the flashing is done.

For more update options see user manual.