You better go to the department in person to see Diane Moffat or the receptionist. You can get a booklet of Graduate Schedule and Registration Information and a copy of Registration Form there, and make appointments with Moffat and your supervisor or the Graduate Advisor, Roberto Chen-Rangel. Maybe you can do that by phone.
The Registration Form should be approved and signed by your supervisor or the Graduate Advisor. Then you'll meet with Diane Moffat to register at the appointed time on Aug 25 or 26.
As a full time M.A.Sc student, I was told I can register 2 courses/8 credits at minimum, and 3 courses/12 credits at maximum. I think it should be the same for course based M.Eng.