To begin, click on the classes you wish to enroll in. Then click on the gear icon in the upper right corner, and then in the drop down menu, click "Enroll me in this course". When a new page opens describing the course, click in the "enroll me" button at the bottom of the page.
You will now be able to view the course. As the teacher gets content uploaded to the site, there will be instructions to watch a certain video, read certain things, fill in quizzes, etc. You may be asked to mark if you have finished the assignment, or you may need to upload an assignment. You may or may not have live class sessions, depending on the teacher and the course. All of this should be explained on the course page, as the teacher gets content, announcements uploaded and shown to the students at the time the teacher wishes.
If you have questions, leave a chat message for the teacher or the administrator by clicking on the chat icon at the top right of the page and searching for the name of the teacher or administrator...