Hello Pieroowuqu54
It is not possible to add tickets to a SBB account if you didn’t buy them with this account.
Tickets are usually not exchangeable (except some international tickets, see the conditions), but sometimes refundable. You can find information about refunds here:
https://sbb-tickets.cc/en/help-and-contact/refunds-compensation/refunds-compensation.html
Kind regards
Dahniel