Immediately after <head>, add the following code:
<script src='http://alexgorbatchev.com/pub/sh/2.1.364/scripts/shCore.js' type='text/javascript'></script>
<script src='http://alexgorbatchev.com/pub/sh/2.1.364/scripts/shBrushErlang.js' type='text/javascript'></script>
<script src='http://alexgorbatchev.com/pub/sh/2.1.364/scripts/shBrushXml.js' type='text/javascript'></script>
<link href='http://alexgorbatchev.com/pub/sh/2.1.364/styles/styles/shCore.css' rel='stylesheet' type='text/css' />
<link href='http://alexgorbatchev.com/pub/sh/2.1.364/styles/shThemeDefault.css' rel='stylesheet' type='text/css' />