You should have received an "invitation" to this wiki in your email. Setting up an account should be pretty simple -- sorry to make you go through the hassle, but I think in the end this is probably the easiest way to do it.
Once you're logged in, there are two ways to post a question. The first way is if you're commenting on something posted here on this site. You can do it by hitting "add a comment" at the bottom of any page on this site. The second way, if you're commenting on something that doesn't have its own page here, is by just adding it as a comment to this page. Be sure to identify the text you're commenting on, in that case.
If you can't figure it out, email me your question and I'll post it. Please do this at the latest by the night before class. If you can't find the email I sent, click "request access" (upper right, this page).