After installing Jekyll, create a repo named username.github.io in your Github account. (username is your Github username). Then go to your terminal:
➜ code jekyll new username.github.io
➜ code cd username.github.io
➜ code git init
➜ code git add .
➜ code git commit -m 'First commit'
➜ code git remote add origin [email protected]:username/username.github.io.git
➜ code git push -u origin master
That's it. Github will automatically publish your site at http://username.github.io. -- Pretty cool stuff.