Enable SNMPv3 in the Unifi Controller (Settings > Services > SNMP) and define a username and password.
In Observium, go to Devices > Add Device
Hostname: IP or hostname of target device.
Protocol Version v3
Transport UDP
Port 161 (default)
Timeout 1 (default)
Retries 5 (default)
Auth Level authPriv
Auth Username username defined in Unifi Controller SNMPv3 settings
Auth Password password defined in Unifi Controller SNMPv3 settings
Auth Algorithm SHA
Crypto Password same as auth password field above*
Crypto Algorithm AES
*May not actually be required.
