CAlling APPMAin (rezise flash whit browser)

I find this package in http://drawk.wordpress.com/2007/04/15/fluid-flash-layouts/

package
{
 import flash.display.*;
 import flash.events.*;
 import flash.utils.*;
 
 public class AppMain extends MovieClip
 {
  public function AppMain()
  {
   stage.addEventListener(Event.RESIZE,onResize);  
   stage.align = "TL"; // Top left align the stage
   stage.scaleMode = "noScale";  // items do not stretch to fit
  }  
  public function onResize(event:Event)  {   // In the event call a method to move the items   // or, call each item here to be sized   movieToBeCentered.x = stage.width/2;   movieToBeCentered.y = stage.height/2;   movieToBeCentered.scaleX = stage.width * .5;    // ... etc    } }}

I creat a file call AppMain.as, now how can i call inside the flash?

Please advise
Thanks