AS3 assign class to movieclip - AN EASY QUESTION

programming flash
1

Hello Gurus!

I have an AS file with the following code:

package {
import flash.events.MouseEvent;
import flash.events.Event;
import flash.display.MovieClip;

public class btnButton {
	
	public function btnButton(btn) {
		btn.buttonMode = true;
		btn.addEventListener(MouseEvent.ROLL_OVER,btnOver);
		btn.addEventListener(MouseEvent.ROLL_OUT,btnOut);
		btn.addEventListener(MouseEvent.CLICK,btnClick);
	}
	private function btnOver(e){
		trace("over");
	}
	private function btnOut(e){
		trace("out");
	}
	private function btnClick(e){
		trace("click");
	}
}

}

How can I attach this to a MovieClip within my FLA file?

Many many thanks

Lex