When it comes to HA and vCMP, the vCMP hosts are configured as standalone devices. You only configure HA on the vCMP guests.
As to vCMP guest specific configuration, think of the following configuration items: hostname, mgmt address, vlans, non-floating self IP-addresses, route domains, trunk configuration.
Other configuration items like nodes, pools, virtual servers, static routes and floating IP adresses can by synchronized.
You can easily start building the new cluster member, add it as a trusted peer and to the device group. Try to sync to the group from the member that holds the complete configuration. If it fails to sync, it will give you a hint what could be missing on the new cluster member. Then you add the missing configuration item, and try to sync again.