Go to
http://webassign.net/login.html
Scroll down and click on the box saying, "I have a class key."
Type the code for your section listed in
http://www.math.mcmaster.ca/~haskell/math1a_10-11/courseoutline.pdf around the bottom of the first page. Then, choose to log-in if you have a preexisting account on WebAssign or register a new account. Either way, you have to use your MacID as your username, and "mcmaster" as the institution. (You don't have to worry about the password!
)
Now, you should be enrolled in the online section of the course.
After you log-in, choose your prefix (it should be EWB-MTB) and type the rest of your access code, and you have access to the assignments.