Create the private feed
Open Business Settings, choose Integrations, then create the iCalendar feed. Copy the URL when it appears because it should be treated like a password.
Add it to a calendar application
In Apple Calendar or another compatible application, choose the option to add a subscribed calendar, then paste the private URL. The exact wording varies by application and device.
Rotate or disconnect the feed
Rotate the feed if its URL may have been shared with the wrong person. The previous URL stops working after rotation. Disconnect it when the subscription is no longer needed.