In this video, we'll deploy our site to Netlify.
Head over to Netlify and sign up. You'll probably want to use your Git provider so you can integrate with your repositories. You can either upload the public folder that results from gatsby build or click "New site from Git" and choose your project repository. You can leave all of the default options and click "Deploy site." Within just a couple minutes, you'll have a real, live site!
To learn more about Netlify, check out Deploying Apps to Netlify by Preston Lamb.