Unfortunately, the GUI isn't quite up to playing with ornaments at the moment (unless it's there as a normally hidden option, Mark?).
Basic steps are:
1. enable the plugin (put ornaments into the plugin list)
2. add \stylesheet{standardborders.sty} , assuming you're going to use them - you're welcome to define your own!
Decide... ornaments for zrule, or ornamental borders around textboxes, sidebars, or everything?
\zrule|cat="VectorianRule3" thick="5"\*
Here is an example for textborder, which uses a slimmed-down version of what you can set for a sidebar or a cat:titlebox|esb / cat:headingbox|esb