The main boat docks are in Thun and Interlaken. Both towns can be reached by car or by train.
How to get to the boat dock
There are many towns to board the boats. The main boat docks are just outside the rail station of Thun, and just outside the rail station of Interlaken West. Both places can be reached by car but it's easier by train.
Some other towns where you can board the boats are Oberhofen and Spiez. Note that the map does not show all the stops as they differ per trip. If you have the time, the complete trip from Interlaken to Thun or vice versa is recommended to fully enjoy the beauty of the lake and the surrounding Alps.