Go to Property Settings / Booking Engine / Your Engine Link.
Open this link to configure Booking Engine on your Facebook Account.
Click on Add To Facebook Page button, log in to your Facebook account and select the page to which you want to add your Booking Engine.
You will see configuration number, copy it and paste to FrontDesk Master, then Save the settings.
Go to your Facebook page and open Manage Tabs tool.
Find Book Now option and move it to the top of the list.
After adding booking engine to Facebook make sure you reorder the tabs to make BOOK NOW always visible: