What is this thing?
That's described on the about page.
Who can use this?
The software itself is open source - check out the about page.
Much of the Marlboro course content is visible to anyone, however, page editing is restricted to faculty and students.
How do I log in?
If you're enrolled in a course, then your faculty member or site admin (that's Jim at Marlboro) should have set you up with an account. Click the "log in" button at the top right of the window.
What can I do once I'm logged in?
That depends on which course and page you're visiting, and whether you're a student or faculty in that course.
How do I edit a page?
If you have the rights to modify a page, you'll see an "edit" tab near the top of the window.
What you can type after you click "edit" is described on the markdown syntax help page.
Once you're editing a file, you can drag files from your desktop onto its "drop files here to upload" region to upload attachments, which are placed into a nearby folder. If the page is named "foo.md", then its attachments will be pladed in "foo.attachments".
What's with these folders?
The files for each course are in a hierarchy of folders, just as they are on your computer. Visiting the url of a folder shows you the files in that folder, unless an index.html or index.md file hides the listing.
If you have the rights to edit that folder, then clicking the "edit" tab allows you to upload files to the folder and create subfolders. Faculty can also set access rights.
If in doubt, ask Jim. :)
The old help pages might also be of some use.