HI,
Yes, you have to configure master-ip in both the locals and join to the network. once the relation is established, master will push the configuration ( only AP-Group, local DB and Policies ) and both the local will sync with the master.
Step 1 : Configure both locals with required Controller IP,VLANs, VLAN ip address and routing if required
Step 2 : Configure the master-ip, ex : masterip 172.16.1.1 ipsec <IPSec key same as configured in the master>
Step 3 : Connect the local controllers to the network and check whether the IPSec is up or not (show crypto ipsec sa or show datapath tunnel)
I'm sure the above will help you to configure standalone as locals
Please feel free if any further help required.