How to Configure a Calendar’s General Access Permission Settings in Google Calendar

Here you can make the calendar available to the public or anyone in the organization by checking the boxes. You can also configure the permission level to the right.

Click Get shareable link to send a link that allows someone with access permissions to add the calendar by going to the link in their browser.

As far as the sharing levels you can select on the right go, they do the following:

See only free/busy (hide details) only lets people check when you are busy with other events and see when you have free time, but they can’t see any details of your events.

See all event details lets people find details for all events except those marked private. They can also find the time zone setting for the calendar and subscribe for email alerts when events are created, changed, canceled, replied to, or coming up.

The other two options should be grayed out. You can only grant such permission levels when sharing directly with specific people, as shown here.