Step 2: Go to Menu > Apps > Google Workspace > Calendar. Requires having the administrator privilege.
Step 3: Click Sharing Settings
Step 4: In the External Sharing options for Primary Calendars section, choose how your users can share their calendars with people outside your organization.
If you do not want us to write back to your Google Calendar, select “Share all information, but outsiders cannot change calendars”.
If you want us to write responses and/or change the calendar event color choose “Share all information, and outsiders can change calendars”.