From your booking.com extranet (1) click on "Account" at the top right corner of the page, then (2) click on "Connectivity provider"
(3) Click on search
(4) Type "CiaoBooking", then (5) click "Ciaobooking"
(6) Click Next
(7) Verify your data (you don't need to fill in the ID from provider), (8) Tick the checkbox to accept the terms and conditions (you can click on the link to read more), (9) Click on "Yes, I accept"
Done! We will contact you and we will connect all room tipe for you!