You've booked BLT - are you DVC members booking on points? If you are you do not have to book a package to get a dining plan. Because you are not annual passholders or Florida residents you do not qualify for Tables in Wonderland.
If you are a DVC member you must call Member Services and ask them to add one of the three dining plans to your reservation. You do not have to buy anything else and you will pay for the dining plan when you check in.
If you have a cash booking, you can get a dining plan only if you book a Magic Your Way package including room, tickets and dining. You cannot get a dining plan unless it is part of a package reservation, so you would have to convert your room only reservation to a package reservation and add tickets as well. The Disney reservation line can do that for you.