Thank you for your inquiry.
When you buy a Swiss Travel Pass you do not automatically have an account with us.
If you want to make an account with us to personalize your purchases you can register here: swisspass.ch
If you already have an account and have forgotten your password, you can request a new one here: swisspass.ch
Seat reservations can also be purchased as a guest without having an account online on our homepage: Seat reservations in trains and dining cars | SBB
All Infos about reservations: Help with seat reservations for Switzerland and Europe | SBB help & contact
Please note that some trains like International and Panorama trains can only be reserved at an SBB counter or by phone:
Tel. 0848 44 66 88
(available 24/7, sometimes you may be required to wait)
You can also make guest purchases on the SBB Mobile App, i.e. without having to have a Swiss Pass login, i.e. an account with us.
I wish you a lovely day
Kind Regards MelanieD