If you would like your users to self-register, you can provide them with a link to a login/registration page.
To find this page, navigate to "URL Access Links" under the Manage > Settings > Configuration Settings. There you will find a section called "General Master Account URL Access Links." Either of the first two links will take your users to the login/registration page.
If it is their first time using Gauge, they will simply click "Register To Get Started" then follow the on-screen instructions.