I was looking at the plugins for displaying JavaScript code, and concluded that Prism was most likely going to be the best one to use for what I wanted. I was a little puzzled by some of the explanation of what was needed to get Prism up and running properly (http://plugins.b2evolution.net/prism-plugin). There's a section on the page that runs as follows:

Note: the XHTML validation must be set to "Basic security checking" at Blogging Permissions, and the HTML posting must be "Not Allowed" in the current collection ( Post options ) in order to get this plugin fully operative.

Whilst I had no problem finding the first setting mentioned on the XHTML validation, but I can't locate the second one in the post options. Either I'm looking in the wrong place, or the manual is little behind the times,; I'm just not sure which.