Sitetree is just a jar file so all you need to do is drop it on your classpath somewhere. The real decision is how to configure it. You have two major tasks.

1. Implement the SitetreeFactory interface. This class takes configuration from storage (wherever you want that to be), sends it to the parser, and returns a Sitetree for the session. SimpleSitetreeFactory can be used for simple sites but for more complicated ones you will want to implement your own.
2. Configure your JSP container to send requests to the RootServlet. For advanced usage you may want to write your own RootServlet or use Sitetree in some other way.

Both of these tasks are discussed in more detail in the Usage section.