Go to Guest Relations in the Marketplace section, I did it a couple weeks ago-super easy! It's across from the scrapbooking store if I remember correctly.
If your staying at a resort just jump on the DTD bus. But, you must be at a resort to get a DTD bus (not from the parks). If your driving just look for the many DTD signs or a Typhoon Lagoon sign which is right across the street from it.