Install
Use pathogen and clone this into your $VIM/bundle
directory.
If not using pathogen, copy the contents of doc
into $VIM/doc
and do a :helptags $VIM/doc
to generate the tag list.
Using
When editing a Java file:
:help XMLConstants
I find it helpful to do:
set keywordprg=
in my .vimrc
so that the "K" command will look up the javadoc of the class I'm on