AS3 -AttachMovieClip is no more!!

yea, it always sounded old, AS3 works without it. A common way of including an graphical object to the stage follows. I include a way of embedding an image straight away:

package {
   import flash.display.MovieClip;
   import flash.display.StageAlign;
   import flash.display.StageScaleMode;
   public class Test extends MovieClip {
      // be sure this is pointing to an image in your hardrive
      [Embed(source='\images\whatsup.jpg')] public var MyImage:Class;
      public function Test() {
         stage.align     = StageAlign.TOP_LEFT;
         stage.scaleMode = StageScaleMode.NO_SCALE;
         var img:MyImage = new MyImage();
         addChild(img);
      }
   }
}

Just attaching a symbol from the Library to the stage here:

package {
   import flash.display.MovieClip;
   public class Test extends MovieClip {
      public var MyLibrarySymbol:MovieClip;
      public function Test() {
         var mc:MyLibrarySymbol= new MyLibrarySymbol();
         addChild(mc);
      }
   }
}