https://using-wordpress.gatsbyjs.org/
Example site that extends the using-wordpress example and demonstrates how to build Gatsby sites that pull data from the WordPress CMS API using Advanced Custom Fields.
IMPORTANT NOTE: This example site won't keep working if you switch the WordPress site to one of yours. It's meant as a learning resource. Try starting from scratch with a site created by gatsby new and start copying over parts from this site starting with gatsby-config.js.