Those instructions refer to using the Google App Engine Launcher. If you have it, the deploy button looks something like this:
https://cdn.tutsplus.com/active/uploads/legacy/tuts/104_gaeProxy/Tutorial/deploy_small.png (a blue circular icon with an arrow on it)
While those instructions still work if you have Google App Engine Launcher, Google Cloud has likely evolved quite a bit since those instructions were written. It is likely they don't point to Google App Engine Launcher anymore. I would try following the Google Cloud docs for deploying.