I think there is a missunderstanding on what you need to travel by train in switzerland. In order to be allowed to take a train, you need nothing more than a ticket. The Swiss Travel pass is your ticket for essentially all trains, busses, interurban busses, tramways, ships, and so on.
Optionally, you have for some trains the possibility to add a seat reservation. This is not a requirement for travelling onboard the train. Seat reservations can be bought independently of tickets.
For very few exceptions, (Namely the Glacier Express, the GoldenPass Express and a few other select panoramic trains), seat reservations are mandatory.
The Swiss Travel Pass is, when bought online, issued in the form of a QR-Code which the ticket controll staff can scan to check the ticket. As for all personalized tickets, an ID can and might be asked for additionally in order to check if the person travelling matches the person for whom the ticket is valid. If you did not yet get a QR-Code, check with the thrid-party reseller how you can get one.
Note that the Swiss Travel Pass is not the same thing as a Swisspass. A Swisspass is a credit-card-format card onto which yearly and monthly regional travel passes can be loaded used almost exclusively by residents. It is not needed (not even possible) to add the Swiss Travel Pass onto the Swisspass.