THE APP SHOWS THAT I DO NOT HAVE A CREDIT CARD SO IT WON'T LET ME BUY MORE CLASSES.
FollowFrom the Base Screen, click the gear icon in the top right corner. Then scroll down to Billing Information. If there is a red "!" it means the app can't get your credit card information from MBO. Click Billing Information and follow the instruction to update your credit card from the app.