Create a copy of this site on your own GitHub account. After the clone is ready you can create/edit your own content on your page. If you dive into you can even customize the page because you have complete control over all sources. Try it...
Login to this page with your GitHub account. Enter the name of your blog (xyz.github.com) and a page slogan. Click on fork... The status bar should go to 80% very fast. This means everything is fine. It then waits for GitHub to render the page which can take up to 10 minutes (normally it is faster).
After your page is ready you can revoke the permission to access the repository in your github account settings...