As Far as I know, We need ANE file to show Ad in Flash. Hence if you want to continue woth Flash 5.5 you need to recreate a bit of your stuff and add this File as swc to Flash Builder Mobile Project.

Either you can use Flash CS6, which have ANE file adding facility. (Right and Best Option)

Let me know which Option suits you, so I will provide you more help

Ritesh Newal

http://code.google.com/p/flash-for-mobile/

qq讨论群：56892018

version for android http://code.google.com/p/flash-for-mobile/

version for iphone and ipad https://github.com/lilili87222/admob-for-flash

this is a actionscript native extension for developer to ad advertisement to their air mobile application run on iphone or android.it very easy to use

admob for flash android this lib enable you to add admob ad to your flash air application to add native advertisement to your actionscript3 application you just need to do four step

1.replace D:\Program Files\Adobe\Adobe Flash Builder 4.6\sdks\4.6.1\lib\android\lib\resources\android-res.jar with android-res.jar

2. add this config to -app.xml

<android>

<manifestadditions>

<![CDATA[

<manifest android:installLocation="auto">   

<uses-sdk android:targetSdkVersion="11"/> <uses-sdk android:minSdkVersion="8"/>   

<uses-permission android:name="android.permission.INTERNET"/> <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

<application>

<!-- <activity android:name="com.google.ads.AdActivity?" android:configChanges="keyboard|keyboardHidden|orientation"/> --> <activity android:name="com.google.ads.AdActivity?" android:configChanges="keyboard|keyboardHidden|orientation|screenLayo ut|uiMode|screenSize|smallestScreenSize"/>

</application>

Unknown end tag for </manifest>

]]>

</manifestadditions>

</android>

3.add this config to -app.xml

<extensions>

<extensionid>

so.cuo.ane.Admob

</extensionid>

</extensions>

4. add code to your android air application like follow 

test1(); private function test1():void {   

var admob:Admob=Admob.getInstance(); if(admob.isSupported){   

admob.setUnitId(gid); admob.dispatcher.addEventListener(AdEvent?.onReceiveAd,this.adHandler); admob.dispatcher.addEventListener(AdEvent?.onFailedToReceiveAd,this.adHandler);

// admob.showRelation(AdMobAlignment?.ALIGN_BOTTOM,AdType?.BANNER); 

admob.show(50,100,AdType?.BANNER);

}else{   

trace("not support");

}

}

protected function adHandler(event:AdEvent?):void {   

trace("receive ad");

}