There are two ways to send your booking request to the hotel.
After you have found the hotel of your choice. You click on booking request, fill in the form and click on "send booking request". Afterwards the hotel in question will send you a confirmation.
Contact the hotel in question by telephone and mention that you are in possession of a valid Hotelcard.
Please note that the Hotelcard is personal, it is made in your name, so it is not transferable. The person who owns the Hotelcard must be part of the stay.