Hello Quoatauquiwh24
Is it a family member and you need another Swiss Family Card? You can only get it on-site at the SBB Travel Center in the station. It cannot be added online.
If the child is not a family member, you can purchase a Day Pass for Children.
https://www.sbb.ch/en/tickets-offers/tickets/day-passes/day-pass-children.html
Or a Junior Card (available at the SBB Travel Center) for CHF 30, valid for the entire stay.
You should not make public your ticket details, to protect your privacy and avoid ticket fraud. We will delete the image again.
Kind regards,
Roland