the closest airport is Bern which has only a limited number of destinations, otherwise the best airport is Zürich International Airport from where trains (with one change) can be taken directly from the airport (approx. 2h).
Timetables can be found, in four languages on: www.cff.ch
From stations Interlaken West or Ost, it is about 15’ minutes’ walk to the congress venue.
Use GPS. Parking is limited.