If you are already registered on the Walt Disney World site you need to login first. If not register and then login. Once logged in, you will see 'My Disney Vacation' in the top right corner. If you hover your cursor of this, a drop down list will appear. Click on 'Dining Reservations' at the bottom of the list. This will open the Dining Reservations page. You enter in your dining confirmation number and the phone number you made the reservation against. You can select 'Retrieve Multiple Reservations' for as many reservations as you have made. It will open up another confirmation number/phone number line each time you click it. Once you have all of your information entered click 'Retrieve Dining' and it will bring up all of the reservations.
I hope this helps.