To set requires confirmation configuration, you simply need to:
Log in to your cal.com account
Open the event-type from the
cal.com/event-type
page and click on -> Advanced tabEnable the toggle that reads
Requires Confirmation
From here, -> Select Always if you want it to be an event-type that requires confirmation at all times -> Select When booked with less than {{num}} {{time}} notice to only make it an opt-in event type when a booking is made within the selected/configured time-frame.