At this point, you have enough information to begin picking your own way through the JAXP libraries. Your next step depends on what you want to accomplish. You might want to go to any of these lessons:
If the data structures have already been determined, and you are writing a server application or an XML filter that needs to do fast processing, see Simple API for XML.
If you need to build an object tree from XML data so you can manipulate it in an application, or convert an in-memory tree of objects to XML, see Document Object Model.
If you need to transform XML tags into some other form, if you want to generate XML output, or (in combination with the SAX API) if you want to convert legacy data structures to XML, see Extensible Stylesheet Language Transformations.
If you want a streaming Java technology-based, event-driven, pull-parsing API for reading and writing XML documents or want to create bidrectional XML parsers that are fast, relatively easy to program, and have a light memory footprint, then see Streaming API for XML.