how to handle movielclip of stage by class

For each clip in the library that you want to control from your class you set the linkage properties and give the item a class name. The class name you give it allows you to instantiate it from code.

So, say you have a document class, and want to put clip A on stage in the constructor, and you've given it a class name of LibraryClipA:

package{

     class MyDoc{

          private var clipA:LibraryClipA;

          function MyDoc(){

               clipA = new LibraryClipA();

               clipA.x = 100;

               clipA.y = 100;

               addChild(clipA);

          }

     }

}