Make sure that all forum support questions get posted in the support forum and not in the Modifications forum...
You need to unlock the registeration system and allow members to register normally. Then you can set the membership activation feature so that the administrator is needed to activate new accounts.
To do that, login as admin and then go to the admin area and scroll down... on the left side you'll see General Admin, click on the link titled Email Configuration Setup, scroll down and set to on, the option titled 'Administrator Member Activation'
Once done, new members accounts status will be Not Active, until you [administrator] activate them.
P.S. You [the administrator] will be notified by email when a new member registers, with a link to activate that new account. In order for such feature to work, a mail compnent must be installed on the server such as CDONTS. CDOSYS, JMail, etc...