How to Use a Theme in an Existing Site
While you can get started quickly with a Gatsby theme starter, you can also install a Gatsby theme directly to an existing Gatsby site. Gatsby themes are plugins, so you can install and use them like any other Gatsby plugin.
Like any Gatsby plugin, Gatsby themes are Node.js packages, so you can install them like other published packages in Node using npm or yarn, including local workspaces.
gatsby-theme-blog is the official Gatsby theme for creating a blog.
To install it, run in the root of your site:
Depending on the theme, there may be theme options that can be configured via
gatsby-theme-blog can take a number of different options. All of them are documented in the theme’s README file.
To learn how to further customize a theme, check out the docs on Gatsby theme shadowing.
Public Gatsby themes are published on npm for anyone to use. You can also publish private themes for use by your organization. Examples of private theme package hosting include the npm registry and GitHub Package Registry.