Talk to the Front Desk. They should be able to add your Reward number to your entire stay. If you leave without adding it, you can go to the Marriott website, logon to your account, go to the Marriott Rewards page, look at the column on the right for the "Missing Stay Request" link. You'll need a copy of your hotel statement (not just the credit card bill) to submit along with the form that you will print from the webpage. Drop it in the mail and once verified, your credit should be posted. If you have any questions, the 800 customer support line is really helpful too.