You can download the Java API publishing kit from this website.
Alternatively, you can download the Java API source code. To build this code you will also need to download some third party libraries and edit the build.properties file to reference the location you downloaded them to.
You can also download further documentation on the SiteRefresh JSP Tag library as well as Javadoc documentation for the core API.
To Install:
The publishing kit file contains a "WEB-INF" directory with contains that can be placed over the WEB-INF of an exploded .war file. That will allow you to immediately begin coding against the API.
Click on one of these links to see sample code to perform the indicated operation: