Go to the Github page and download the simpleslider.js file. Don't forget to download the touchswipe.js and transit.js if you're going for a complete (and still simple) slider.
Now you have the files you can include them in your header.

<script src="http://code.jquery.com/jquery-1.10.1.min.js"></script> <script src="http://code.jquery.com/jquery-migrate-1.2.1.min.js"></script> <script type="text/javascript" src="transit.js"></script> <script type="text/javascript" src="touchSwipe.js"></script> <script type="text/javascript" src="simpleSlider.js"></script>