Please note that it's a bit difficult to describe the behaviour if you are not that used to it. Just install it into your system and try it out (see below).

The plugin is available in source form in jEdit's CVS repository.
A pre-compiled binary can be found at the IQ Computing web site or in the beta plugins download area on the jEdit Community web site.

To install the binary Jar file, just copy it into jEdit's "jars" directory, then restart jEdit.