well....you do the course on teh interweb!!11!!one!!1....duh lol
i've taken three so far
our school uses this system called WebCT. You log on, and you get to see the syllabus/lessons/etc.., email of your professor, as well as emails of all classmates, and then there are links for assignments that become available at a specified time, then you usually have until midnight before the link goes away, to complete the assignment. For tests, quizzes, etc....usually you click the link, then you have 60 minutes to complete the assignment, before it automatically closes.
theres really not much to it. everything is the same...but instead of going to class lectures, you do independent reading. And test/quizzes are all done online at specific dates/times specified in your syllabus..