It's the same as your original confirmation code. You need to keep the confirmation # and passenger name, you don't have to link it to your Rapid Rewards number. Go to 'View Ticketless Travel Funds Balance' in the Travel Tools tab, input the code and passenger name, then they will show you the amount you have on it. When you book another flight, there is a space where you can redeem credits toward the purchase before you check out.