Livestream allows Enterprise customers to set a single password for any event on their account, allowing only desired viewers to see the event.
To do this, navigate to the event you would like to password protect and click the Editor icon.
Navigate to Privacy.
Check Protect my event with a password and type in a password in the text field that appears. Be sure to save your settings.
Now when a viewer goes to your event page, they will be prompted to enter a password. They cannot access your event until they enter the password your set for this event.
If you have a Vimeo Premium account, see Vimeo's Help Center to learn about password protection.