To add the book button on your website please follow these steps.

1) Login to Google My Business account -

https://www.google.com/intl/en_ca/business/

2) Scroll down to "Website" on the left side menu

3) Click on "Edit"

4) Click on "Button" and select "make appointment"

5) Open Yocale and login inside your account. Navigate to "Booking Page" top right corner and copy your "Online Booking Widget" link

6) Go back to Google My Business and paste it in the Appointment Links field

7) Press the checkmark button and finally the publish button

Your finished!