Are you talking about the Disney Visa reward dollars?
If you are, there are two separate steps involved. First you have to request a Disney Reward Redemption Card from Visa. You can also get them at various WDW locations - not sure about DCL as I have always ordered mine ahead of time. I order one with the minimum amount (I believe it's $20) so there isn't a valuable card floating through the USPS system. Once you have that physical card you can go online to Visa's website and transfer as many Disney reward dollars as you wish to that card. At that point you may use the card as you would any other Disney gift card. In the past, the reward cards had an expiration date, so you had to be careful to only transfer as many dollars as you would actually use within that timeframe. I was just looking at their website as I need to transfer some myself, and it appears that may not be true anymore.
GET UP TO A $1000 SHIPBOARD CREDIT AND AN EXCLUSIVE GIFT!
If you make your Disney Cruise Line reservation with Dreams Unlimited Travel you’ll receive these incredible shipboard credits to spend on your cruise!