First, use AdMob to get your unit ID for your package name. Add this to the Android project settings and add a “Show Ad Banner” blueprint node. This should be all you need.
If you want to try a test ad without connecting to AdMob servers, you can a test device in GameActivity.java in updateAdVisibility(). Look for:
AdRequest adRequest = new AdRequest.Builder().build(); // add test devices here
and change it to:
AdRequest adRequest = new AdRequest.Builder().addTestDevice("deviceserialnumber").build(); // add test devices here
and replace “deviceserialnumber” with the device id from “adb devices”.