Self-enrolment is the method whereby users can choose to enroll themselves into a course, either immediately by clicking "Enrol me in this course" or by typing in an enrolment key they have been given.
Step 1: In your course, click the Participants tab.
Step 2: From the dropdown select click Enrolment methods.
Step 3: From the drop-down menu select "self enrolment". Make sure self-enrolment is enabled (has its eye open) and then click the edit icon on the right.
Step 4: Add your enrolment key in the box provided. (Click Unmask to see what you are typing.)
Step 5: Click the 'Save changes' button.