This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
You "call" an action class by specifying action="/myAction" in an html:form tag. This causes the Struts ActionServlet to call the action class when the form is submitted. If you're trying to call a class from the browser without submitting a form, that's called AJAX, and is something you'll have to spend some time learning about if you want to do it.