How do I get to Stresa from Murren via train? I do not see that option.
Kennann, where are you looking?
The rail system is a network of interconnections, like roads are. You will never get by car from a small place in one country to a small place in another without turning at at least one road junction. Same for trains. Except for local journeys or big city to big city, expect to change trains, possibly multiple times.
It takes two trains just to get from Mürren to Interlaken (the mouth of the valley), because Mürren is on top of a mountain and only reachable by cable car. Two or three more to get to Stresa.
But YES, you can get from any rail station in Europe to any other.
To find trains, go to the SBB (Swiss Railways) website: https://www.sbb.ch/en
And enter Mürren to Stresa, and a date and time (up to December 2019), and it will find trains.
Finally, make sure you spell place names correctly. This could be your problem.
It is Mürren. The second letter is a ü, NOT a u, that is a different letter. If you don't know how to get a ü on your computer use the alternative spelling Muerren. Murren is WRONG and will not work.