You have asked your question in the German-speaking SBB Community. We do have an English-speaking community here.
Regular point-to-point tickets are good for any connection on the day of the ticket’s validity. Point-to-point tickets do not include / guarantee a seat.
On Swiss trains, there is usually free seating, this is why your ticket does not come with a seat assignment. Swiss trains are a form of mass transit, similar to suburban trains in other countries. As a result, you are welcome to take any vacant seat in your respective travel class. If you want to sit next to someone you don’t know, it’s courteous to ask if the seat is available before sitting down.
You will see once you are here how easy it is to use the Swiss public transport.
Should you reserve a seat? Except for certain panoramic trains (PE), seat reservations on Swiss trains are completely optional and not very common. Swiss people usually make seat reservations when they would like to eat in the dining car, when they travel as a group of 10 or more, or when many travelers are expected.
→ If you still want to reserve your seat, kindly note that this is possible for IC, ICE, EC, IR, RJX, and TGV connections only: Seat reservations in trains and dining cars | SBB.