When you go into WDW Dining - there is a spot where you can "associate" your dining reservation with your resort reservation. Select a restaurant you want to book, and then right above where you would enter the date for the ADR, there's a paragraph about associating your reservation.
I made ADRS 180 days out, but have been messing around with them ever since and today made a lunch reservation for Le Chefs du France and changed a Cape May breakfast without too much trouble. Don't know if it will be much busier on Monday with the general release of the free dining or not.