First, log in to manage your pass. Then visit the FlexiPass Tours page. When you click any of the booking links, you'll be taken to a page with the search fields pre-populated for you - just select your preferred date, number of people and click Search.
On the search results page, select the tour service and click to purchase any extras like entrance fees and meals. At the checkout we'll deduct the hours from your pass and you can pay for the extras.