You can do it manually -
SOL13649: Creating a device group using the Configuration utility
Generic instructions from my experience and memory:
pre-work - ensure the new device has all needed local device and network configuration. ensure there's a working NTP server configured on each F5, ensure each f5 has a valid device certificate, reset device trust on each F5 (Device Management | Device Trust | Local Domain, Reset Device Trust (generate new self-signed authority). make sure you've backed up your configs and that you can sustain an outage during the timeframe that you decide to configure HA (never know what will happen)
- Specify config sync address on each device - Device Management | Devices, click on "self" | Device Connectivity | Config sync - specify that local address that you want each device to use for config-sync operations
- Specify network failover addresses on each device - Device Management | Devices, click on "self" | Device Connectivity | Network failover - add local IP addresses that you want each device to use for network failover communication - usually at least one self-IP-address and the management address of the local device
- Specify mirroring address on each device - Device Management | Devices, click on "self" | Device Connectivity | Mirroring - select the local IP address to use when any type of mirroring is configured in the F5 configuration
- On primary device, add second device to device trust peer list - Device Management | Device Trust | Peer List | Add... - enter information of second device. once complete, check that primary device exists in secondary device's device trust peer list (should happen automatically)
- Create device group on primary device and add both devices - Device Management | Device Groups | Create... - create a Sync-Failover group and add both Devices. once complete, check that the device group exists in secondary device's device group list (should happen automatically)