I'm back from my stay. The gift card needs to be collected in Disney Springs. Just approach one of the cast members there and ask.
dining credit is listed in the letter, there is no indication about how it will be paid.
For the dining credit I received an e-mail with a digital card [which could be saved to Google or Apple Pay] . At the restaurants they will scan the bar code.
However a HUGE word of warning....I discovered that all of my credit was gone after just using the card twice for a snack and a small meal at Pop Century.
I phoned the contact number listed in the email, because people at the reception desk did not have a clue about these dining card.
The lady on the phone would only give me a list of restaurants where my dining credit was spent (and needless to say I never went). When I asked for further explanantions, the line went dead.
Looking more closely at the bills I noticed that just one of them was scanned to my dining credit card. The other bill had a different card number (and a different remaining balance) on it.
Again I tried in vain to point this out at the reception desk. I was 200 dollars in the loss at that moment.
As I was quite early entering Epcot that day, I decided to try Guest Services. First things they did was phone the contact number again and recite all the restaurants again.
In the end I did manage to get the message across that the barcodes on the cards do not seem to scan properly and that this was obvious from the numbers on the bills.
So word of caution again, always check your balance. This will have happened to others as well! They solved it by giving me a physicial gift card for the full amount again.