You will have TWO flat-rate envelopes. The FIRST is going TO the consulate. Both the priority mailing label and the signature confirmation form will be addressed to the consulate, but the mailing label should have YOUR return address in the "FROM" portion.
INSIDE the first envelope, you will include a SECOND flat-rate envelope with a return priority mail label and the signature confirmation form addressed to YOU. The consulate's address will go in the "FROM" portion of the mailing label. Don't forget the necessary postage!
Here's what these should look like.
Call Mike Kruchoski (480-5000) if you have any questions.