Please help me to figure out how to add adMMob to my Actionscript 3 app. There isn't a well-written documentation on how to do it. I only found a youtube video that explains it but still it was not well and fully described . for the bits and pieces of information that I gathered, I managed to construct the following code, however it errors. Please help to reconstruct the code so I get it to work.

1. First I got Pozirk's AdMob Air Native Extension from github
2. I installed the AdMob.swc and the AdMob.ane files in the Advanced ActionScript settings
3. I created a class file called which contains the following code:

PHP Code:
package {   
import flash.display.MovieClip;
_admobAdMob = new AdMob();
public class 
Main extends MovieClip{
        public function 
//> initialization of AdMob

4. I added this line to the script, it's sitting on the top root and not part of a function or anything else. I'm not sure if it's supposed to be nested somewhere.

PHP Code:"ca-app-pub-3940256099942544/6300978111"AdParams.SIZE_SMART_BANNERAdParams.HALIGN_CENTERAdParams.VALIGN_BOTTOM); 
with this above settings when trying to compile the code I get the following error message:

", Line 1 5006: An ActionScript file can not have more than one externally visible definition: _admob, Main"

Why I'm getting this error message?
Is this code is proper to run adMob?
am I missing something?