To use git: 
1. Make a repository on github 
2. Open a terminal, decide which directory you want the repository 
$ git clone https://github.com/username/username.github.io 
$ cd username.github.io
Modify the repository how you wish. When you're ready to push it to github: 
$ git add --all 
$ git commit -m "Some message describing the update" 
$ git push -u origin master 
That's it!