Admob help

So Im trying to get Admob working in a test project . I loaded in admobpackage 3.1.3 and imported all worked fine but when I tried to insert example code its not finding using GoogleMobileAds;
using GoogleMobileAds.Api; libaries

Plugin is more easy to use.It contain all resource reqired by this plugin.

You can find the whole tutorial here

Admob Into Unity