Configurate the communication XMPP or MUC between octo bridges

Dear all,
According to the answer in
Loadbalancing Octo + tracking feature from @Boris I understand that we can config the communication between Octo bridges via either XMPP or MUC. Would you please show me how to configurate this feature?
Many thanks

The second part of this post gives an example: How to add the secondary jvb to main jitsi-server

Thank you very much @damencho. As I understood, with such MUC configurataion the new version jicofo can calculate better the trafic of each vb in order to have better load balancing (Loadbalancing Octo + tracking feature) .