Hello arturobazan_
One person has to purchase the pass on their name and can use it throughout the day.
The three other travel companions cannot use it independently, the Friends Day Pass is only valid when they travel together with the person who has purchased the travel pass. Consequently, the three travel companions must purchase a separate ticket to the place where they all meet and from where they continue their journey together.
You can find the conditions on the respective product page:
https://www.sbb.ch/en/tickets-offers/tickets/day-passes/friends-day-pass-youth.html
Kind regards,
Roland