Step by step
Open Bookings
Go to Bookings and choose New booking.
Turn on Walk-in booking
In the dialog, enable Walk-in booking. The hint explains that the customer is on site, the slot is confirmed immediately, and no confirmation email is sent.
Fill service, staff, and customer
Select the service, staff member, time, and customer details as usual.
Create booking
Choose Create booking. The list can show the type as Walk-in so you can tell it apart from Online bookings.