There are several ways of closing the availability. Of course, you can simply block the beds on the BedView, but if you really want to be sure that the room is closed then we recommend doing it in Availability & Rate Calendar.
Simply check the Close Room checkbox and click SAVE.
This will trigger actions such as CLOSE ROOM for Booking.com, DELETE AVAILABILITY for Hostelworld and STOP SELL for Expedia. They are provided to make it easier for you to quickly close the room.
Note, however, that if you have some arrangements with the portal such as "Minimum Contracted Rooms", the portal may not accept closing the room or changing the availability to "0", please double check in your back office.