Password protection is only available for paid users. If you’re on a free (Basic) plan, you can upgrade anytime.
To enable a password, go to Settings > Sharing. You’ll see a list of all existing calendar links. Click on the Edit button next to any link, then complete the password section for that link.
You’ll see a key symbol next to any calendar link that is password-protected.
When a password-protected calendar link is used, the user will be prompted to enter the password before the calendar will load.
To see all the steps for password-protected calendars, click here.