You'll need the JSON as a project file and also need to use the AJAX object to correctly load a JSON to array.
I've added an example of a very simple array editor that I would create to fill in an array for any game I was making. In the "Load Array" layout & event sheet 2 are the correct events for loading data into an array from JSON. You'll have to run the layout in debug mode to see that the array is filled from my saved JSON.
Hope that helps.
Oh and you'll need the latest beta for anyone who wants the CAPX