Getting your environment ready before the fun starts

This chapter is the boring one. Before you start writing or customizing, there are a few things worth knowing upfront so you do not get stuck on something avoidable later.
GitHub Pages offers a set of official themes you can apply with a single line in _config.yml. The full list is at pages.github.com/themes.
Each theme has a repository where you can see the default layout files. That matters because customizing means overriding those defaults, and you cannot override something you have not found yet.
The theme this site uses is Leap Day. To apply it:
# _config.yml
remote_theme: pages-themes/leap-day@v0.2.0
plugins:
- jekyll-remote-theme
If the official themes are too constrained, you can also base your site on any public GitHub repository that is a valid Jekyll theme by referencing its user/repo path the same way.
By default your site lives at username.github.io. If you want a custom domain, the setup takes about ten minutes.
A records pointing to GitHub’s servers:
185.199.108.153
185.199.109.153
185.199.110.153
185.199.111.153
CNAME record pointing www to username.github.io.CNAME at the root of your repository containing just your domain name:
yourdomain.com
DNS changes can take a few hours to propagate. If the SSL certificate does not appear within an hour of the DNS resolving, go back to the Pages settings and save again to re-trigger the check.
A few repositories worth bookmarking before you start:
If you are starting from scratch, forking an existing site is often faster than starting from a blank template. You get working navigation, layouts, and configuration that you can adapt instead of building from the ground up.