Making a Course Visible
When you are done enabling the self-enrolment method (and specifying a fee for the course if applicable), you can publish it by changing the course's visibility to "Show".
Step-by-step Guide
Go to the course in question
Go to Course Administration > Edit Settings
Change "Course Visibility" to "Show"
Click on the "Save and Display" button at the bottom of the page
Important Notes
Courses are visible by default so unless you hid the course while developing it, this step may not be required.
It may take a while once a course is published for it to be available to all users.