In this video, we talked about the "book appointment" flow.
You need first connect your calendly account in the integration, and then you can set up the buttons which can pull the event from your calendly account.
Make sure to connect to your Calendly event.
Also, another improvement you can do is to add extra steps to verify the email & phone numbers in the flow.
P.S: Once you get the email in the chatbot, the Calendly booking page will auto-fill the user's name & email address without you do anything.