In your main xwork.xml, provided swaf-user-mgt-VERSION.jar is in your classpath, you can do:
todo: make this package abstract, and have users define the name space of their choice for it.
You'll also need a valid xwork validation.xml file at the root of your classpath. It is not provided by swaf-user-mgt, so that you can define your own validators for your actions. However, you should make sure you include at least the default ones defined by xwork, or at the very least the one used by swaf-user-mgt. (check the sources for details, then)