Preconditions: 
- The device must have a valid date/time

Step by step:
1) Enable Firmware update via "System / Security / Configuration / Firmware-Update"
2) Open <ip-address/swupdate> with the connected operating device (Smartphone or Laptop)
3) Enter credentials for user "maintenance"
4) Drop ".swu" file into the "Software Update" box
5) The device will update the firmware and restart after the update is complete

Note: The SWUpdate web server page might look frozen because the firmware update feature is disabled after the update. 
To check if the update is complete, just refresh the web server page or look at the device display.