A master realm contains trustees, which are the user accounts. Within a realm, you can also create groups and trustee containers (OU, Domain, Country, and Locality).
In Library Manager, expand Trustees.
Right-click Realms and select Add.
In the Add Realm dialog, select Master.
In the Add Master Realm dialog, the only required field on the Account tab is the RDN (relative distinguished name), which is the name of the realm. You'll return to this dialog to configure the Libraries tab after you've created the facility administrator account and a facility.
For the RDN field, enter a name for the master realm.
Select OK to continue.
The Library Manager now displays the new master realm under Realms.