It's a small station. If you have a lot of luggage, be ready at the train exit with your luggage when you pull into I. Ost. Because yo have to go up and down some stairs and walk a short distance through a pedestrian tunnel, hauling a lot of luggage can be a nuisance. However, you'll see a lot of other tourists doing it, and most will likely be trying to catch the same train that you are.
Standard train change time for Swiss trains is 4 minutes at most stations
Did you look at the track numbers for arrival and departure?
Larger stations have "trafimage" station plan maps available on the SBB website.
I.O. is too small to have one. Instead, I have linked to another map of the station plan
This link shows a map of the station from a SwissTopo map, but unfortunately does not have track numbers labelled: Nonetheless, you can see that there are only 3 platforms. You will come in on track 8, which is the local line running in and out of the Lauterbrunnen Valley.
You will leave on track two.
map.geo.admin.ch/?topic=ech&lang=en&bgLa yer=ch.swisstopo.pixel karte-farbe&layers=ch.bav.ha ltestellen-oev,ch.swisstopo.swiss tlm3d-wanderwege&layers_visi bility=false,false&X=1 71294.00&Y=633004.00&z oom=10
Google Maps offers a live view full 360 degrees image. Zoom in on the station in Google maps, then click on the little man and the blue spot on the map to get full 360 degree rotatable image., if this long below link does not work.
www.google.com/maps/pl ace/Interlaken,+Switze firstname.lastname@example.org,7.86 96124,3a,75y,338.29h,9 0t/data=!3m8!1e1!3m6!1 s-qkLeVH--4QA%2FV3N6b53FUAI%2FAA AAAAAAIpA%2FBueBfx046A wXCLS1zYTNClZ1JGydI8OA wCLIB!2e4!3e11!6s%2F%2 Flh5.googleusercontent .com%2F-qkLeVH--4QA%2FV3N6b53FUAI%2FAA AAAAAAIpA%2FBueBfx046A wXCLS1zYTNClZ1JGydI8OA wCLIB%2Fw203-h101-n-k-no%2F!7i8704!8i4352!4m 5!3m4!1s0x1453996a3192 1a05:0x9c111af14c02be0 0!8m2!3d46.6863481!4d7 .8632049!6m1!1e1 and
You will come in from Lauterbrunnen on the track furthest to the south (track 8) . After you exit the train, you will go down stairs and walk about 30-50 meters through a pedestrian tunnel, go back up some stairs and will be on the correct platform. Watch the track numbers on the signs.
Once you are on the platform, they won't leave if they see you getting on the train.
If you don't have a lot of luggage, you can get on at any car,and walk through the center aisle to a car with open seats. If you have a lot of luggage,that is very hard to do, but not impossible. Then it might be to better to walk along the train a bit to one of the cars that is a bit farther from the stairs where you come up.
When you get to Spiez ( not Spies) you come in on track 2 and leave on track 3. It also is a small station. Their is no Trafimage map, but I am 99% sure from looking at other maps that your tracks are on the two sides of one platform.
Just walk across the platform.
Hope that helps.