you create these groups where you manage your users.
If you are using the db plugin and creating your users with kopano-cli (or kopano-admin), then you also use this to create groups.
If you are using an ldap backend (e.g. when using ActiveDirectory or on Univention) then you are also managing your groups in there.
In the case of UCS your simply create group from their web ui and then in the group details mark it as a “Kopano group”.
Relevant chapter from our documentation: https://documentation.kopano.io/kopanocore_administrator_manual/user_management.html