Data send to Blynk

Continuing the discussion from HTTP Integration with BLYNK:

I am strugling with passing data from TTN to Blynk.
Can anybody help me. It is not clear how the payload from my sensornote must be handled in the HTTP integration.
In the URL :
The value in this casse 77 is send to the Blynk server and pin V5 is updated. But how can I send the payload of the sensor?

The payload is included as a data element - the HTTP performs a POST with a JSON file

Thanks Nick,
How is the data included in the JSON file, do I have the payload to encode with a payloadfunction?