Beyond needing a car with a logbook, etc. you'll need a CARS regional license. In order to get your license you have to pass a medical, have your first aid, be a club member and pay your money, basically. Here's where you should go to look:
http://www.carsrally.ca/CARSRally/Default.aspx?tabid=94

A word of warning, do not leave this to the last minute. Beyond the extra fee if you're within a week of the event, the license coordinator does not like late applications.

Once your car is fully prepped (cage, seats, belts, extinguishers and the many many other thing you need to have) it has to be inspected by a RSO scrutineer. Most events do not allow this to happen at the event, it has to happen prior to the event. You can contact the scrutineers at scrutineers@rallysport.on.ca and once they approve the car they will issue a logbook that follows the car through its life. It contains info on every performance event entered, the outcome and any significant damage so that event scrutineers can check a car after a crash to make sure it's been fixed properly, etc.