Technically, amateur Canadian players do not need to pay taxes on their winnings. Officially, the tax to be paid on gambling wins is 0%.
With that said, if you keep the winning sum in a bank account and over time it derives interest, that gets taxed.
A specific tax form needs to be filled during tax season. This is known as the T5 and in it, you need to include all the sums derived from wins, and that have accrued interest.