PhoneGap / Cordova File Download

gistfile1.js

var fileSystem; 
var documentRoot; 

function onAppReady() { 
    window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, gotFS, function() {}); 
} 

function gotFS(fileSystem) { 
    fileSystem = fileSystem; 
    documentRoot = fileSystem.root.fullPath; 
} 

function downloadFile() { 
    var filePath = 'PATH TO YOUR FILE'; //For example: http://example.com/bigmovie.mpg 
    var localFileName = 'YOUR FILE NAME'; //For example: bigmovie.mpg 
    var ft = new FileTransfer(); 
    ft.download( 
        filePath, 
        localFileName, 
        function(entry) { 
            alert('File Downloaded'); 
        }, 
        function(error) { 
            //Handle the error 
        } 
    ); 
} 

document.addEventListener("deviceready", onDeviceReady, false);

Do you know how I can get that to work for the inAppPurchaseManager. I have a github here with my example code on how I do it when unlocking products, but my main goal is to be able to download the magazine from my server then view it on my app. Any help you can give would be awesome! https://github.com/usmart/InAppPurchaseManager-EXAMPLE