Note: If you want your learners to create accounts on your site and have access to your courses, then you first need to enable Email-based self registration so they can create accounts, and then enable self enrolment within your course(s) so they can enrol. These are two separate steps.
Self enrolment is the method whereby users can choose to enrol themselves into a course, either immediately by clicking “\enrol me in this course” or by typing in an enrolment key they have been given. The enrolment plugin needs to be enabled by the site admin in Enrolment plugins and has to be enabled within the course. The manual enrolment plugin has to be enabled in the same course as well.