Hopefully, you decided to have the exchange certificates/vouchers mailed to you. You will need the numbers off the back of the voucher to order the DDE.
Keep in mind that the expiration date for the DDE will be 12 -13 months from the day you order it. That is different from the AP - your year of admission for the APs won't start until you exchange the voucher for the actual pass.
Once you have the AP in hand, you just call the DDE office. THe CM there will help you.
You can find the DDE telephone number and hours of operation on this site:
Disney Dining Experience
Best wishes -