Set Days/weeks as unavailable ?

Hello.
You can  make the blank  booking  for such date(s) at  the Booking > Add booking page,  to set such date(s) as unavailable.

In the Booking Calendar Business Small or higher versions you can use “Auto fill” button at the top toolbar in the Booking > Add booking page to make the fast blank booking in 3 mouse clicks. 

If you need to  set  different available dates for the different seasons, then  it’s possible in the  Booking Calendar Business Medium or higher versions.
Check more about this feature here: https://wpbookingcalendar.com/overview/#availability
Watch it in this video guide https://wpbookingcalendar.com/help/booking-calendar-video-season-availability/

Kind Regards.

Hello.
In this version for making the dates as unavailable, you need to create some (blank) booking(s).
Kind Regards.