To work as a Flight Dispatcher in Canada you must write and pass the Transport Canada exams and you must be at least 21 years old. Transport Canada offers a study guide in TP12153 for the topics you will need to know. There are a few choices for schools offering Flight Dispatch courses to help you prepare for these exam topics.
Expect at least a few months of on the job training after you are hired, and a competency check before you are issued a Dispatch Certificate. If you leave your job as a dispatcher your dispatch certification will expire in two years, at which point you will have to rewrite the Transport Canada exams.
Click this link for a Google search on dispatch schools.