You must be Canadian citizen first! if yes, you should x the choice in the front page of your tax return which means your information including address will be sent to Election Canada. Before the election date, you should receive a letter from Election Canada to inform that you are on the voter list and where is the vote station for you and when you can go there to vote. If up to the election day you have not received the letter, you can go to the vote station with your citizenship card and ask for immidiate registration and vote!
Good luck!