Hi Valeria!
In most cases, it's not necessary to have your
Walt Disney World dining reservations linked to your resort reservation & dining plan in advance. Your hostess will ask you if you are on the dining plan upon check-in at the restaurant, and your server will ask you again when he or she greets you at your table.
Where it does become advantageous however, is that at the resort level, a Concierge Cast Member or front desk Cast Member will be able to print off your dining reservations for you if requested, upon check in.
Having the dining reservations added to your resort reservation after the fact is very easily done. Simply call the Dining Reservations line at (407) WDW-DINE (3463) and speak to a Cast Member there, advising them that you need assistance linking your dining to your resort reservation. Be sure to have at least 1 of your dining reservation numbers handy at the time. They'll confirm your reservation list with you and tie it all together!
Have a Magical vacation Valeria!
Kirsten