Be sure to get off the train at the Interlaken Ost station. Get on the train going to Lauterbrunnen. Be sure to get on the front section. The back of the train breaks off at Winderswil to go to Schynige Platte. Each section of the train will have a sign showing you where it goes.
At Lauterbrunnen, get off the train. If you are going to Gimmelwald or Murren, there are two ways to go. The quickest is to take the bus to Stechelburg. After you get off the train at Lauterbrunnen, go to the right of the station, with your back to the tracks. The bus stop is just to the right of the gondola station. The bus ride takes around 10 minutes and will take you directly to the gondola station at Stechelburg that goes up to Gimmelwald, then Murren and ultimately to the Schilthorn. The Swiss Pass stops paying full fare at Murren.
If you want to take the gondola at Lauterbrunnen, it goes up to Grutschalp. From there you will get on a train (in the same small station). It will take you to the south end of Murren. To get to Gimmelwald, walk all the way to the other end of town to the gondola station. This gondola will take you to Gimmelwald or up to the Schilthorn.
If you are going to the west side of the valley, at Lauterbrunnen get off the train from Interlaken Ost and onto the cog train to Wengen. If you are going up to the Jungfraujoch, just stay on the train to Kleine Scheidegg. This is where you will get on the train up to the summit. The Swiss Pass stops paying full fare at Wengen.
If you are going to Grindlewald you will get off the Lauterbrunnen train at Zweilutschinen and onto another train to Grindlewald. The Swiss Pass will work all the way.
Hope this helps. Good luck