Role - Users
The Users panel lets you choose users that should be assigned to this role.
For example, if you have created a role for junior administrators, you can use this panel to assign any users who should function as junior administrators to the role. You can also assign a role to a user when you create that user.
To manage users with this panel, your current role must be assigned the Role.ManageUsers authorization and the role you are currently modifying must also be assigned the Role.ManageUsers authorization. If both of these conditions are not true, the arrows that allow you to move users between columns are dimmed.
Available Users, Selected Users
In the list under Available Users, select users who should assume this role and click the right arrow, which moves your selections to the Selected Users list on the right.