Start searching and reading the many many posts that have discussed this topic through and through.

I know it sort of is easiest for you to ask us here what to do...but it would be nice if you can read all that has been discussed many many times and then decide how and where you'd like to start the trip.

Since you are in Canada, it would be no problem for you to issue the ticket there for a ticket originating elsewhere at that country's RTW fare. You still however need to go there to start your journey. Your best bet is perhaps engaging the services of a good travel agent who knows at least what to do with RTW fares.