Repository permissions
One answer
An admin can open up a user editor (either in the web or in the Eclipse UI) and they will see a "Repository Groups" section in Eclipse, or a "Repository Permissions" section in the web. From there they can assign/revoke permissions such as: "JazzAdmins", "JazzProjectAdmins", "JazzUsers", "JazzGuests"
If you are talking about permissions on a project area scope, this usually involves adding the user as a member of the project area (or team area), and then assigning them specific roles (as roles are the way to customize permissions at the project area level).