im sure they did tell him in the adivisin session. not only that, but common sense would of showed you where to fill in your desired electives on the form you were givin. You need to read the info in the enrolemt pack that tells u step by step how to sucessfully enrol in subjects.
plus - either your Academic advision, the enrolement paperwork, the blue helping shirt people, the signs around the enrolment centre pointing to a room "HOW TO FILL IN YOUR ENROLMENT FORMS" sessions were run every 30 mins:\ all of those things would of told you how to fill in your subjects and how to add/minus electives
But do not stress - still plenty of time. Print off a variation of program form on the uws site (check a thread below this one - someone pasted the link) - and simply write out the name of the elective u want to do - what semester, and then circle ADD on the form. Easy.