Json data - not able to query


I am new to Grafana…that said,

I installed Grafana
I installed the Simple JSON plugin
I created a JSON data source connect with a sample file from this site

Now how can I query the data - when I try to build a query - I dont get any fields in the dropdown.

Am I missing something here…
Is there anything else to install for API’s or something or am I doing something wrong!

Would appreciate any input - Thx