Triyng to get eventdispatcher trigger listener in multiple instances

hi.
im migrating to as2 from as2. and im having a lot of understunding problems regarding scopes and how to refer to functions, classes, etc
i used asbroadcaster in as2 to register m,ultiple listener with a single event.
now, with as3 im trying to use EventDispatcher to do the same. but it doesnt work. in fact, i dont know really how does it work.
in as2 i create an asbroadcaster in root
then i add listeners to it from within multiple movieclips, so when the event was thrown from anywhere the listeners registered for that event where triggered.
how do i acompplish that in as3?
in advance thanks