You need an API key for "Simple API Access".
-You get it via https://code.google.com/apis/console/ and then "API Access".
+- You go to https://code.google.com/apis/console/
+- Then you go to "Services" and activate "Google+ API".
+- After that you go to "API Access".
+- At the bottom of the page you see "Simple API Access".
+
+The value after "API key:" is the key that you need.