You need to finalize your contractual relations with Booking.com. Check the messages from Booking.com for instructions. If you are not sure what exactly Booking.com expects you to do contract Booking.com support.
= Import Properties from Booking.com =
You can create a new property and rooms in Beds24 from a property in Booking.com. The Booking.com hotel and room IDs will be automatically added to the channel manager settings.