Struggling to implement admob

import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;
import com.google.android.gms.ads.AdSize;
import com.google.android.gms.ads.MobileAds;

I am attempting to implement banner ads into my app, following this old thread:

I am getting the same error as the op, but am struggling to understand (what the following mean/how to do them)

  • “and instead of installing the SDK automatically (by processing) download it and install manually”
    • where do I get the SDK? Where do I put it?
  • “download the SDK of course from Android, without AS.”
    • what is AS?
  • “extras/google/googleplayservices/libproject/libs”
    • I don’t have this folder path