Haughoifues63
What you posted above to the public Internet is a 1st class Basel - Montreux ticket valid all day for the usual, most direct route, not a reservation: It doesn’t mention any specific departure time, coach or seat number.
Tickets and seat reservations are always two separate things. As already mentioned, that ticket is not valid on the Golden Pass Express, as that one means quite a (more expensive) detour between Bern and Montreux via Spiez - Gstaad.
So if you want to take the Golden Pass Express (GPX) that day, follow Danhiel’s recommendation, cancel that 1st class ticket and get the cheaper full fare 1st class Saver Day Pass instead. Current price for May 11th is 97.00, it will cover any train between Basel and Geneva according to your mentioned travel plans and also be your ticket for the GPX train. Warning: Not refundable in case of a change in your travel plans.
The (recommended) seat reservation for the GPX tourist train is a separate thing, which you’ll manage directly with the train operator on https://www.gpx.swiss/en/
Make sure to buy the seat reservation only, as you already have a valid 1st class ticket with the Saver Day Pass.
Reservations on all other (SBB) trains are generally not needed, unless maybe during peak commute times when leaving Basel or heading to Geneva.