On this tab, you can view the Global level users and also assign ${Role.Plural} to ${User.Plural}.
 
To execute the icons in the Actions column refer Generic Features.

To manage the User Roles, click on the Manage User Roles icon to manage user roles.
The Manage User Roles dialog box, select the ${Role.Plural}, the ${User.Name} can have access rights to and click on Save.

Click on a ${User.Name} to view its properties.