With user groups, myDBR allows you to assign privileges to groups of users in addition to individual users. This will make maintaining the report privileges easier (see Access rights). In 'User Groups' preference you can maintain the user groups (add/delete/rename) and add users to specific groups.
You can simply add a group by entering the group name and press 'Add group'-button. If you are planning on linking users in a group dynamically (see 'Data-driven user classification' in Access Rights) choose the group name accordingly.
Once a group is added you can add user to it. This can be done by pressing the Edit Group -button next to the group name. This will open a search field where you can enter a username (or part of it). From the resulting list you can check the users to be added and then press 'Add selected user(s) to group xxx'-button. A user can belong to more than one group.