It's incredibly easy to create new pages in Gatsby.
In src/pages, create a new file called about.js.
In this file, import React and add a simple function. Your code will look like this:
import React from "react"
export default () => <div>About Gatsby</div>
If it's not already running, run the development server with gatsby develop. Your new page should be located at localhost:8000/about.
Up next is your first assignment!