Place a call on printRegistrationForm() where you want the form to appear. Probably the best use is to create a new 'custom page' script just for handling these user registrations. Then put a link to that script on your index page so that people who wish to register will click on the link and be taken to the registration page.

When successfully registered, a new admin user will be created with no logon rights. An e-mail will be sent to the user with a link to activate the user ID. When he clicks on that link he will be taken to the registration page and the verification process will be completed. At this point the user ID rights is set to the value of the plugin default user rights option and an email is sent to the Gallery admin announcing the new registration.

NOTE: If you change the rights on a user pending verification you have verified the user.