To block dates in calendar you can use one of these 2 ways.
Add bookings manually from Calendar
Go to Dashboard -> Properties -> Edit Property -> Calendar
Select booking dates by clicking on the dates (selection is red)
Booked dates are blocked in the calendar, and in front end booking form:
How the booked dates look in the booking form:
How to delete booked period
You can mark dates as booked from All In One calendar as well -help https://help.wprentals.org/article/all-in-one-calendar-view/
In all in one calendar owner form looks like this.
Import an ICAL feed with booked days (from Airbnb, Google Calendar etc)
In order to make calendar and booking unavailable can use the option that allows to Owner to add ical feeds to listings and add an ical from a platform (like Airbnb) that has the option to block all dates in the calendar and mark it as booked.
Help for Ical feed feature: https://help.wprentals.org/article/icalendar-import-export/
Example of how to block dates on Airbnb and export ical from their platform with all dates booked.