Help making a MovieClip to be a popup

Hi guys

I have a a scene in the stage as the background with a text saying to press anywhere...

When someone clicks on it, a MC will appear asking something...

My question is... how can I make this MC to be a pop up instead of being on the stage?

This is what I have, so far:

private var initialScreen:Loader;

private var pos:TextField;

private var pos_holder:Sprite;

private var fmat:TextFormat;

..............................................

initialScreen = new Loader();

initialScreen.contentLoaderInfo.addEventListener(Event.COMPLETE, onComplete);

initialScreen.load(new URLRequest("1.jpg"));

fmat = new TextFormat();

fmat.font = "Times New Roman";

fmat.size = 105;

fmat.color = "0x0000FF";

pos = new TextField();

pos.defaultTextFormat = fmat;

pos.autoSize = TextFieldAutoSize.CENTER;

pos.text = "Click anywhere";

pos_holder = new Sprite();

pos_holder.addChild(pos);

private function onComplete(e:Event):void {

initialScreen.width = stage.stageWidth;

initialScreen.height = (stage.stageHeight * 1.5);

initialScreen.x = 0;

initialScreen.y = ((stage.stageHeight/2) - stage.stageHeight);

addChild(initialScreen);

pos_holder.width = stage.stageWidth * 0.8; // 80% width relative to stage

pos_holder.scaleY = titulo_holder.scaleX; // To keep aspectratio

pos_holder.x = stage.stageWidth / 2.2;

pos_holder.y = (stage.stageHeight * 0.2);

stage.addChild(titulo_holder);

initialScreen.addEventListener(MouseEvent.CLICK, popup);

}

private function popup (e:MouseEvent):void {

var question1:MovieClip = new MovieClip();

question1.graphics.beginFill(0xFF0000);

question1.graphics.drawRect(0, 0, 100, 80);

question1.graphics.endFill();

question1.x = (stage.stageWidth * 0.40);

question1.y = (stage.stageHeight * 0.70);

addChild(question1);

                    }

**** I haven´t finish making the MC yet, since it will have a couple of buttons and a text... but I need it to be like a popup and now it just appears on the background

Thanks!!!