1) Login to Booking.com and go to ACCOUNT->CHANNEL MANAGER. If you do not see this option contact Booking.com and tell them you want to use a channel manager.
2)Click the Start button and search for BEDS24. <embedvideo service="youtube">https://www.youtube.com/edit?o=U&video_id=VYzWI-PDVYk</embedvideo>
3) Complete the rest of the on screen instructions.