Completely lost!

Hello and I hope someone out there can help.  I am a new user to Microsoft Bookings, and my question is:  How can I have bookings that are not automatically assigned to a staff member.  I have tried changing the business hours and also changing the staff availability, but nothing I do seems to put the booking into the 'No Staff' calendar - what I want to be able to do is then assign these appointments to whoever is around at the required time (this can vary).  Any suggestions would be most gratefully received.

Colleen