You can display T&Cs and other information valuable to the guest either on the page where you include the booking engine, on the search page of the booking engine, or let guests accept the terms through a checkbox in the booking engine.
To have the text display on the search page of the booking engine, go to Settings -> Languages & texts -> Terms & Conditions.
To add an accept checkbox (with a link pointing to the terms & conditions), go to Settings -> Booking engine -> Manage booking engines and click the edit button. Enter the URL where your terms & conditions can be found. Guests will then have to accept the terms and conditions by ticking the checkbox.