Follow the step-by-step instructions there. Do NOT ask me where to get a rom for the game, you're on your own there. Also any comments related to such questions will be deleted.
While we're on the subject, all comments with spoilers will be deleted also. I will be monitoring the comments very closely, and I really don't want anyone who hasn't seen it to have the story ruined for them.
Now sit back, relax, and enjoy the adventure that is Mother 3!