Don't forget to call <script>hljs.initHighlightingOnLoad();</script> this one load Syntaxt Highlighter.
It's very easy to use this highlighter. If we write any code in post then we use <code> </code> tag for this. Use <pre><code>Your Code</code></pre> for highlight syntax.
Syntax Highlighter latest version has auto language detector system. Language define is not necessary for this. You will get a lot of themes and styles of Syntax Highlighter. Open styles directory here you gel lot styles, use as you like. If you like GitHub style then links up GitHub stylesheet. Change stylesheet <link rel="stylesheet" href="/path/highlighter/styles/default.css"> to <link rel="stylesheet" href="/path/highlighter/styles/github.css"> This is available for 166 languages and you could use 77 themes for styleing.