Place your code on the page and surround it with tag. Set name attribute to code and class attribute to one of the language aliases you wish to use.
... some code here ...
NOTE: One important thing to watch out for is opening triangular bracket <. It must be replaced with an HTML equivalent of < in all cases. Failure to do won't break the page, but might break the source code displayed.
An alternative to is to use
Extended configuration
There's a way to pass a few configuration options to the code block. It's done via colon separated arguments.
... some code here ...
Finally, to get the whole thing to render properly on the page, you have to add JavaScript to the page.