Since version 7.039 you don’t need to alter any setting or do other preparations to import a JSON feed of any format. Just add the link and the plugin will do the rest of the job – it will recognize the internal structure (any), will parse it and format it for you automatically.
Also there is a new feature in this version. Now you can import ZIP-archived feeds (XML, JSON) and CSV files. The plugin will unpack them on the fly.
P.S. You don’t have to update anything manually. The plugin updates itself automatically within 24 hours.