Assign user to a realm.

Hi team, I am trying to assign VLANs to different realms, and only a few users to be part of a given realm. E.g.: user1 and user2 are part of @staff and should be assigned VLAN 123 user3 and user4 are part of @student and should be assigned 98 If a user is not part of a realm, he should be denied. Could you please help me on how I can assign a user to a realm? Thanks for your help. Regards, *Deepansha Gaur*