[Gatsby Ghost Starter] Where are we pulling the home page from our ghost pro website and putting it as a gatsby index page?

I cloned gatsby-ghost-starter repo and changed the ghost.json. I have been looking around it to try and get a grasp of how things work, I was wondering where do we pull the home page from our ghost pro website and make that the home page of our gatsby page? Not sure if it’s in gatsby-node.js or somewhere else. Also is there any tutorails or documentation that walks you through the code in the starter repo?Thanks!