Plugins are used to extend the functionality of Opinio. To add a plugin to Opinio, simply place the plugin Jar file in the Opinio/WEB-INF/plugins. To do this, you must have file system access to the application server. If the plugins folder does not exist, then create it. Most likely it will exist, because a sample plugin is included with Opinio.
Free and commercial plugins are available here:
Plugin configuration will vary depending on the plugin. Some plugins require no configuration at all. Refer to the documentation included with the plugin for more details.
See the appendix creating plugins for information on how to create your own plugin.