Administration of a MUC room mostly consists of managing roles and affiliations. Roles are temporary, and apply until the user leaves the room. Affiliations are permanent, and based on JIDs.
If you have moderator privileges, you can change the role of a participant with M-x jabber-muc-set-role. Kicking means setting the role to “none”. Granting and revoking voice are “participant” and “visitor”, respectively. “moderator” gives moderator privileges, obviously.
The possible roles are:
If you have admin or owner privileges, you can change the affiliation of a user with M-x jabber-muc-set-affiliation. Affiliation is persistent, and based on JIDs. Depending of your affiliation and the MUC implementation, you might not be allowed to perform all kinds of changes, and maybe not in one step.