You must edit your _config.yml file to add Jekyll plugins to your GitHub Pages site.

To add Jekyll plugins to your site, you need to configure your _config.yml file by adding your plugin's Jekyll gem. This is an example of a _config.yml file that has several supported jekyll plugins enabled:

gems:
   - jekyll-mentions
   - jemoji
   - jekyll-redirect-from
   - jekyll-sitemap
   - jekyll-feed

If you don't have a _config.yml file, you will need to create one in the root of your GitHub Pages repository. For more information, see Jekyll's official plugins documentation.

Tip: * Make sure you're using the latest version of the GitHub Pages Gem, which contains these dependencies and plugins.