http://code.google.com/mobile/ads/docs/android/fundamentals.html
followed by the following:
http://code.google.com/mobile/ads/docs/android/banner_xml.html
Basically you add the "publish code" jar to your app, then insert a few lines into your manifest. Then you place the banner into your app where you want.
The one piece that tricked me is that if you simply try to add the sample xml unit to your project you need to make sure that in the main layout (the one that declares the "android" namespace), you need to add the following:
xmlns:ads="http://schemas.android.com/apk/lib/com.google.ads"
