//In your Main class :
public function Main() {
	
	levelManager = new LevelManager(ALevel);
	levelManager.applicationDomain = ApplicationDomain.currentDomain; // to be able to load your SWF level on iOS
	levelManager.onLevelChanged.add(_onLevelChanged);
	levelManager.levels = [[Level1, "levels/A1/LevelA1.swf"], [Level2, "levels/A2/LevelA2.swf"]];
	levelManager.gotoLevel(); //load the first level, you can change the index. You can also call it later.
}

private function _onLevelChanged(lvl:ALevel):void {

	state = lvl;

	lvl.lvlEnded.add(_nextLevel);
	lvl.restartLevel.add(_restartLevel);
}

private function _nextLevel():void {

	levelManager.nextLevel();
}

private function _restartLevel():void {

	state = levelManager.currentLevel as IState;
}

// Note that you must create an abstract class : Level1 and Level2 extends ALevel 
// which extends the State or StarlingState class. From our example :
public class ALevel extends State {

	public var lvlEnded:Signal;
	public var restartLevel:Signal;
	protected var _level:MovieClip;

	public function ALevel(level:MovieClip = null) {
		super();
		
		_level = level;
		
		lvlEnded = new Signal();
		restartLevel = new Signal();
		
		// Useful for not forgetting to import object from the Level Editor
		var objectsUsed:Array = [Hero, Platform, Enemy, Sensor, CitrusSprite];
	}

	override public function initialize():void {
		super.initialize();
		
		var box2d:Box2D = new Box2D("Box2D");
		add(box2d);
				
		// create objects from our level made with Flash Pro
		ObjectMaker2D.FromMovieClip(_level);
	}
}