How to connect application to get a database file from google cloud sql

few days ago, I try to create an application that can connect to my google cloud sql database

from the following URL :https://developers.google.com/appengine/docs/python/cloud-sql/developers-guide#use_with_lang

I got a basic Hello World! ( Follow step 1,2)

So , After that Can you suggest me more ,how to connect and get existing  database files ?

Because when i try to follow next step ,  difficulties are more ...  (What is the next step when i do with Python? )

Best regards.