WordPress has a setting called Membership: Anyone can register. If you check this box, then ANYONE can register on your site. But what if you want to approve memberships before they become active?
In order to require WordPress Admin approval for new users, you’ll need to install the New User Approve plugin. Once you have the plugin installed, it automatically takes over the registration process.
When a new users registers, WordPress admins receive an email notifying them that a new user needs to be approved. To approve a new user, go to Users > Approve New Users.