HA configuration on new standby unit

Hello Experts,

I have a currently standalone unit .... running 11.2.1 version with HF9. This box is configured with partitions / RouteDomains / VLANs / Trunks and other LTM configuration....

We have got a new box for HA and want to configure it as a secondary box

What would be the easiest way to configure the secondary box....the boxes will sync configurations and be failover peers

Thanks....