This flow template uses an endpoint to populate flow data dynamically. You can follow this guide to implement your endpoint https://developers.facebook.com/docs/whatsapp/flows/guides/implementingyourflowendpoint

To see what data you need to send from your endpoint to show a specific screen, you can find the right snippet from Flow Builder by going to "..." > "Endpoint" > "Snippets" > "Responses"

For example, for the first screen "DETAILS", you need to return a response like this { "version": "3.0", "screen": "DETAILS", "data": { "city": [ { "id": "1", "title": "Light City, SO" } ] }

Don't forget to encrypt the response before returning it. You can refer to the encryption code examples here https://developers.facebook.com/docs/whatsapp/flows/guides/implementingyourflowendpoint#code-examples