In order to book a sparring partner at one of the chosen clubs, you just have to choose the desired court and time-slot on the reservation table (for courts) and tick the checkbox "Book a Sparring Partner" in the appearing reservationdialog window (see screenshot below).
The Reservation has to be at least 3 hours before the start of the reservation, to give your sparring partner enough time to organize himself and to arrive at the club. Your sparring partner will contact you prior to the beginning of the appointment.
Have fun! ;-)