The device will download, install, and reboot automatically. If the device won't boot, use the TFTP recovery mode: Software Downloads - Ubiquiti
: If your device is part of a live production link carrying critical traffic, always test the upgrade on a non-essential unit first. Ubiquiti’s 1.255 is stable for most, but hardware variants exist. Upgrade Firmware Version 1.255 Ubnt -FREE- Download
To avoid security risks like malware or bricking your device, always use official channels: Official Downloads : Only download firmware directly from the Ubiquiti Downloads page Ubiquiti Releases forum UniFi Site Manager : The safest and easiest way is to use the Settings > Updates The device will download, install, and reboot automatically