RVsitebuilder comes with the full-featured authentication system. There are user and admin interfaces separately. So, you can have different business logics for users and admins.
https://yourDomain.com/login , only user can login here.
https://yourDomain.com/admin/login , only admin can login here.
While installing RVsitebuilder, we ask you admin email address and set it up securely. If you forgot password, you can get the new one by requesting from the forgot password page of your site.
In addition, if you create the website from cPanel, you can always single sign-on to the admin area.
You can configure it on admin area / content, click on system page and click login for user and admin/login for admin. You can configure authentication method both user and admin separately.