Facebook allows you to add a booking button to your Facebook page using their "Call to action button".
To add a call-to-action button to your Page:
Click + Add a Button below your Page's cover photo.
Under "Which button do you want people to see click Book Now and then Next
Click Link to website
Paste in the link to your salonMonster booking page
Once the button has been created, you can test your button:
Hover over your newly created button
Select Test Button