See this guide for detailed step by step instructions. https://en.support.wordpress.com/google-docs/ (yup, WP) and https://support.google.com/docs/answer/37579?hl=en
In order to manually create some Google Docs media entities go to /media/add/googledocs.
Also see: https://drupal-media.gitbooks.io/drupal8-guide/content/modules/media_entity/basic_usage.html