You can choose between different airline companies who fly from Oslo.
SAS, Norwegian, Widerø. All these are of course available on internet.
A tip for you outside Norway is to check if there are any of these flying from your home QTH and direct to Bergen.
As Bergen is popular, we advise you to book flights ASAP when you have registered.
The main terminal for train is easily reached by taking the flight train from the airport if you land at Oslo airport to the Central station and catch the train to Bergen from there.
NSB (Norwegian state railway)
You can check the times and prices and also buy tickets on net.
Those coming with their car, can easily reach Bergen. Just remember that in September the snow on the mountain passes may have settled.
If you want to bring your car onboard “MS Trollfjord” , this is allowed. That way you have a car to drive when we reached Kirkenes. But this must be booked ahead of the departure.