Download the struts distribution file from the jakarta apache website, and unpack the distribution. Look inside the webapps/ directory, there are a bunch of war files that can be installed by copying them into your $CATALINA_HOME/webapps/ directory. Restart your server, and you will be able to access the documentation through your web page. e.g. The url that can be used in a default installation of tomcat would be http://localhost:8080/struts-example/index.jsp
After unpacking the distribution, you will need to add lib/struts.jar and possibly the other jars to your CLASSPATH. And also the *.tld and *.dtd files into the WEB-INF/ directory.
JSP 2.0 containers will not require you extract the *.dtd files if you use the correct URI in your JSP pages.