Shelby, it depends on how you booked. If you booked by using the Walt Disney World Travel Co., you must pay in full 45 days before your arrival date. If you booked through the "regular" CRO, you pay upon arrival.
If you are unsure which one you booked through, there are a couple of easy ways to tell which way you booked by the confirmation code, but I forget the exact details, so I won't attempt to explain.
But I know the deposit amounts required for reservations vary. How much was your deposit? If it was $200, then you booked through the WDW Travel Co., and need to have your payment there 45 days before arrival. If you paid a deposit equal to one night's stay, then you booked through the "regular" CRO, and you can pay your balance upon arrival at the resort.
Hope this helps! If not, let us know and we can see if we can help further. This information should also be available on your confirmation letter....I think. Ours was.
Good luck!