Both the source code and the binary packages of RendView come with documentation in HTML format.
The same (but maybe more up-to-date) documentation can also be found online here.

In case the documentation is unclear or wrong at any point, please e-mail the author. Remember that a good program is of little use when the documentation is bad. For me, as the author of RendView, some things may be clear or trivial which in fact are not (for the majority of the users).