External AS to internal AS

im now working for a school assignment of flash game with AS3.0 which allows us to use some source code to help.
however, i found that many source codes i downloaded are in external classes( XXX.as ),
I want to convert it back to inner flash AS… like:

[LEFT]Main.as[/LEFT]
[LEFT]package {

          import flash.display.MovieClip;
          import flash.events.MouseEvent;
          import flash.events.KeyboardEvent;[/LEFT]
             public class Main extends MovieClip {


I have no ideas how to put these code back to flash inner AS,
are the codes in external AS so different from the inner one? or more or less the same so that i can based on the external one to write a inner one?
thanks!!!:cry3:

this is the game i wanna learn…
http://flashbynight.com/tutes/hangman/