Accessibility to features in WhosOnLocation are restricted by User Roles, these are controlled by the users of your account with the Administrator User Role.
Every user will be able to access their own profile, their frequent visitor list, and the pre-register visitor sections of WhosOnLocation, everything else requires a special user role.
User roles are also limited by the Add-ons activated by the Account Owner. If you are an Administrator and cannot assign a certain user role, this is because the corresponding Add-on has not been activated for your location.
Administrators that are limited to certain locations can only grant user roles for those locations, this is applicable as long as the user role is location based.