Hello ysengk1963
You do not have to reserve a seat at all; in Switzerland, our trains use the free-seating approach. Except for the Glacier Express, and the Golden Pass Express, owning the Swiss Travel Pass, you can simply get on any train you want, find a seat in your respective travel class, and have a ride.
Bear in mind that you have to have your passport or ID card physically (no copies / no photos) with you when using the Swiss Travel Pass or any e-ticket.
More information on seat reservations is given in our blog post:
https://community.sbb-tickets.cc/blog/23887-demystifying-seat-reservations-on-swiss-trains-a-comprehensive-guide
Kind regards,
Roland