I believe the original documentation is here: http://media.wu-wien.ac.at/download/xowiki-doc/
There is an updated version of this document here: http://alice.wu-wien.ac.at:8000/xowiki-doc/
Some FAQs here: http://alice.wu-wien.ac.at:8000/xowiki-faq/
Hope this helps?
At nccedu we've been using the xowiki package extensively and are finding it to be a great addition to the OpenACS framework.
Matthew