What is the proper way to add a SharedObject to a .AS file?

Having trouble adding a SharedObject to a .AS file, I am trying to add the users name to the .flv file in red 5 like "username_myfile" I am not sure I am adding the code thats saves the name in the correct part of the class. is there a proper way to add a SharedObject to a .AS file?

-- added:

import flash.net.SharedObject;

package app
{
    import flash.display.BitmapData;
    import flash.display.Stage;
    import flash.external.ExternalInterface;
    **import flash.net.SharedObject;**

    public class DataHolder
    {
        private static var dataHolder:DataHolder;


        public var savedstuff:SharedObject = SharedObject.getLocal("myStuff2","/");

        if (savedstuff.size > 0)
        {
            public var username = savedstuff.data.username;

        }

             public var filename:String = (String(username) + "_myfile");

        public var rtmpPath:String = "rtmp://numbershere.compute-1.amazonaws.com/oflaDemo/";



        public var recorder:Recorder;
        public var navigation:Navigation;

        public var cameraFPS:Number = 30;
        public var cameraWidth:Number = 640;
        public var cameraHeight:Number = 480;
        public var cameraQuality:Number = 88;// camera quality

        public var timelimit:Number = 25;// limit count of seconds

        public var stage:Stage;

        public function DataHolder()
        {
            if (dataHolder)
            {
                throw new Error("Only one DataHolder instance should be instantiated");
            }
        }

        public static function getInstance():DataHolder
        {
            if (dataHolder == null)
            {
                dataHolder = new DataHolder();
            }
            return dataHolder;
        }
    }
}

Remove the conditional declaration of your shared object and declare as usual, ie:

private var savedStuff:SharedObject;

Then, in your constructor:

try {
    savedStuff = SharedObject.getLocal("savedData");
} catch (error) {
    cookiesActive = false;
};

Then check cookiesActive==true to save data to the SharedObject, eg:

if (cookiesActive) {
    savedStuff.data.levelsFinished = 1;
}