There are few ways of doing it:
1. Book Now button
Simply, under any Book Now button you can use the link which you can find in Property Settings / Booking Engine / Install on the website. This is a fully working booking engine!
You can link our booking engine with a BOOK NOW button and make it open in a frame without leaving the website. HERE you can see how it looks like.
In order to obtain this effect you need to paste this code on your website:
Please meke sure to put both parts as described.
Note we can help you with that! Just provide us with the access details to the website.