The local organizing committee cannot provide a booking service, praticipants need to book the rooms by themselves either directly contacting the hotel (links provided below) or through a booking service like booking.com or Expedia. The city centre of Bergen is quite compact, so you can use any hotel there. There are also further links at the visitBergen web page.
Recommended hotels:
Scandic Bergen City (from NOK 2196 for 3 nights)
Scandic Byparken (from NOK 3135 for 3 nights)
Best Western Hordaheimen (from NOK 2792 for 3 nights)
Budget alternative (shared facilities): Marken gjestehus (NOK 870 for 3 nights in 4-bed room, other options also available)
