Leap day is a Jekyll theme for GitHub Pages. And this is my customization.
You can treat this as a beginner and copy all these prepared to your project. (Remove example files by yourself, of course.)
Since this is a project that will customize the original theme project, I didn't fork codes from that and this theme will keep pace with that. On this basis, I do my customization and this is where my versions and updates will be. So even if you're using a old version of this project's release, your website may change as the original theme's changes still.
For more information about how this will take place, see _config.yml.