ActionScript 3.0 :: Create A Square Grid And Add It To The Movie?

I am trying to create a square grid and add it to the movie. When I open the actionscript panel by pressing F9 and when I type the following code,

Code:
var square:SquareClip = new SquareClip();
addChild(square);

Things are working fine (the squareclip is appearing in the movie).Instead when I do this however, I deleted the above code and just create a new instance of Main,

Code:
new Main
and inside Main.as

[code].......

And when I run the code, my square is not coming.