How to call AS from Unity

I'm trying to get this example: http://docs.unity3d.com/Documentation/Manual/flashexamples-callingflashfunctions.html working and I'm stuck (I'm completely new to Unity). It seems simple enough: use ready-made AS classes (e.g. a library) or write my own, write their (dummy) counterparts in C#/JS for other platforms and then just use the class(es). But my question is - how? The code that's at the end: ExampleClass exampleClass = new ExampleClass(); - where do I call it? In what script? Do I import (using) anything?