Hello Yufeemau63
Firstly, welcome to the SBB Community.
You have to use the SBB trip planner to search for point-to-point tickets with Supersaver offers. These are marked with a % sign. However, should you travel from Geneva Airport after you will have arrived by plane, we do not recommend using Supersaver tickets.
https://sbb-tickets.cc/en
Alternatively, you can purchase a Saver Day Pass:
https://sbb-tickets.cc/en/tickets-offers/tickets/day-passes/saver-day-pass.html
Kind regards,
Roland