How do I load data into an Alpaca JS form post-render?

I have an Alpaca JS form that has already been created and want to be able to upload a JSON file that will populate the form. I have spent time attempting this and am unable to find a way to go about this. I know that data can be stored in the "data":{} portion of the form, but I want to be able to populate the data with a selected file.

Thanks.