If you manage your hardware using a UniFi Network Controller, the process is largely automated: Open up your running . Click on the UniFi Devices tab on the left-hand menu. Locate your specific device in the populated list.
(e.g., v6.6.65). A version numbered "1.255" is not standard for current UniFi, EdgeMAX, or airMAX product lines. How to Safely Upgrade Ubiquiti Firmware Upgrade Firmware Version 1.255 Ubnt -FREE- Download
If you’d like, I can: