Name your account the same name as your desired website's name. (If you already have an account, you can change its name.) This site's url is staticwebsiteskeleton.github.io, so the github account name is staticwebsiteskeleton.
The github must be named the following username.github.io. This site's repo is: staticwebsiteskeleton.github.io. This is the same as this sites URL!!
The file must be named index.html. Index.html is your home page/default page/directory page. Without it you will get a 404 not found error.
You can either write html code directly or use notepad or a different html editor and alter your index.html later.
Don't forget to commit your changes. (Scroll to the bottom of the page.)
Type your site's url: [https://username.github.io] into a web browser's address bar.