Visit your listing on https://www.tripadvisor.co.uk/

In the URL bar (when your on your listing) there will be a series of numbers proceeded by the letter d

Copy the numbers after the letter d

Close this pop-up and paste the numbers into the box

Login to your gmail account

Go to your “Google Calendar App”

Click on the arrow next to the calendar you want to embed and click on “Calendar settings” (pictured right)

Copy your “Calendar ID” (pictured below)

Close this pop-up and paste into the box below this link