Hello Dan half moon bay
Good day.
You should have received information how to activate the pass through this website: www.activateyourpass.com
After activating the day, you will get a QR code valid for the activated day (to be scanned by the ticket inspector).
In addition, for the ticket check on board the train, you will need your physical passport or official identity card (no photos or paper copies).
https://www.swissrailways.com/en/buy-swiss-travel-pass-flex
Kind regards,
Roland