Hello jeff and welcome to the SMBO forums! Have you downloaded the game and got it up and running?
If so, you should register for a new account, then login with your newly created account. Next you should create a character and use that character to start playing the game.
If not, you can download the game here:
http://supermariobrosonline.tk/download.htmIf you're having trouble getting the game up and running, please mention any problems you're encountering on the Game Help forums and we will try our best to help you.
Thanks for joining SMBO, and I hope you enjoy your stay!