To configure PicoContainer to handle the dependency injection of WebWork2 actions, refer to the web.xml below. For a start there is a slightly different listener to the one defined in the main page. Also, instead of using WebWork2's servlet, use ours. Everything else from the standard WebWork2 setup is appropriate.
PicoContainer-Web WebWork 2 Demo webapp-composer-class org.picocontainer.web.sample.ExampleWebappComposer picoFilter org.picocontainer.web.webwork2.PicoObjectFactory$ServletFilter picoFilter *.action org.picocontainer.web.webwork2.WebWork2PicoServletContainerListener action com.opensymphony.webwork.dispatcher.ServletDispatcher action *.action index.html webwork /WEB-INF/webwork.tld
The Maven example project is here. Make sure you make and configure your own WebappComposer implementation.
See downloads on how to download the webwork2 module either using Maven or by downloading full distribution.