The store manager needs to set the role FiftyPercenter for those users who should have it.

See also http://www.openvpms.org/openvpms-site-administration/store-ubercart/roles

Note that the store manager role explicitly has permission to set/unset the FiftyPercenter and Subscriber roles for any user.

To set/unset the FiftyPercenter role, access the user - see Finding Users - then edit the user and set/unset the role as desired. See  for example below.

Note that if you do set the Subscriber role (which is normally automatically set as the result of the user purchasing a subscription), then you will also need to set the Initial Subscription Date (accessed via the 'Subscription Information' tab), and the Subscriber role expiry date (accessed via the Ubercart roles block right at the bottom of the Account tab page).