Open Google Calendar on a computer
Sign in to your Google account
In the left panel, find My calendars
Hover over the calendar you want to share
Click the three dots next to the calendar name
Select Settings and sharing
Scroll to Share with specific people or groups
Click Add people and groups
Enter the email address of the person or group
Choose the permission level
Click Send
To share a calendar publicly, go to Access permissions for events
Check Make available to public if needed
Choose the visibility and permission settings
Save your changes
To stop sharing, remove the person or group from the sharing list
To change access, edit the permission level for that person or group