Only allow booking for predefined timeslots

I would like to use Bookings as an event scheduler where there will be explicit events which the customers could see and select which one they would attend.

This means the Bookings calendar should not be open for any timeslots, customers should only see the exact appointments which we announce.

However, I just cannot do that in Bookings. Service is created, I have also added events to the calendar (where only a limited number of participants can book, like max. 8 persons). But the customers cannot see these event slots.

how can I do this?