You are right that the documentation is lacking in some respect (no examples etc.), but it does you tell that this is done by clicking on the "Add Sublocality" button in the "Edit" menu. Then you edit the topmost field and add the Locality Name Field, as explained in the documentation.
However, localities are always a bit difficult, because different countries follow different conventions for organization in the database.
When you say "that this is done by clicking on the "Add Sublocality" button in the "Edit" menu". This is the part I do not understand. From where do I do this. I just need a brief step by step, 1 2 3 . Where do I start at?
If I had a dollar for every time you helped me, I'd be a wealth man.