To enroll in Courses you can click on the courses tab within a community:
You can click on the learn more button on each course card to view more detail about the course and enroll:
After you've signed up and enrolled in your course, you'll be able to access it from the "Courses" tab on your home page.
You can remove/un-enroll from a course at any time by going to the "Courses" tab on your homepage.
When you locate the course you wish to un-enroll from, click the three dots [...] in the top of the course window and click "Un-enroll." You will not lose any work you've completed or badges you've earned if you un-enroll after you have already completed and earned a badge for that course.