The CMS does not manage members or members area access.
Typically the payment processor (CCBill, Epoch, Verotel, Etc.) will work with you and your host to secure the area and to make sure they have control of adding, editing, and removing users based on billing. When you want to add or create an account you will usually do it through your payment processor's interface, as they control who has access to your site.
Contact your payment processor and see what their procedure is and they should be able to advise you best as to how to proceed.
