Travel between Geneva to Wengen

The only way is by train, as there are no roads to Wengen (and it is too far to walk or cycle☺).

Look up times on the SBB (Swiss Railways) website: https://www.sbb.ch/en

"Genève" to Wengen takes between 3h37 and 3h42, and there are two departures per hour. All rail routes in Switzerland, have a minimum of one train per hour.

Thank you Chris. I have looked at the SSB website and it gives me several options for Geneva as a departure point and likewise, numerous choices for Lauterbrunnen, which to my understanding is where I need to stop to reach Wengen. How do I know which ones to choose when selecting my ticket?

Choose the ticket that connects all the way to where you need to go :Wengen

Put in "Genève" to "Wengen"

Don't use any of the ones lower down as they will be bus stops or suburban stations.

As Nigel says, just choose "Genève" to "Wengen".
"likewise, numerous choices for Lauterbrunnen, which to my understanding is where I need to stop to reach Wengen" - why are you entering Lauterbrunnen when you want to go to Wengen? Just put in Wengen.

"which ones to choose when selecting my ticket?" - There is no point in buying a ticket at this stage. Just buy a ticket at Geneva station when you get there, from a machine or the manned ticket desk. Tickets are valid on any train on the date shown on the ticket.
Use the SBB website to show you when the trains run.

I don’t know how many days you’ll be in Switzerland or how often you’ll ride trains but have you seen the Swiss Pass? https://www.sbb.ch/en/leisure-holidays/travel-in-switzerland/international-guests/swiss-travel-pass.html You can buy once in advance and then not have to worry about buying any more tickets (with a few exceptions like some funiculars, but it works on most trains). It was really simple for our family to use last year.