Check this short video:
1) Login as a business owner and navigate to Online booking on the left side menu.
2) Click on "widget link" either on top right corner or in the widget setup section
3) Open another browser tab and navigate to your Google Listing. You will see the blue checkmark and "You manage this Business Profile" if you are logged into the gmail account that manage this listing. If you do not see this message that means you are not logged into the correct account.
4) Navigate to "Booking"
5) Click on "+ Add another link" under the Link to your online booking tools section.
6) Paste Widget URL and "Save"
7) Your finished. The link will be under review but will be accepted shortly.