Add password code to asp.net page

I have a site built in asp.net using vb. The admin section of my site is password protected. I have one admin page which did not have the password code added properly, because of this anyone can access the page. I need someone who understands vb.net to add my password code to this page. The password is set up to have two user types. Admin and Regular. Only admin user type should be able to access this page. Please let me know if there are any questions.