You can either download it as a gem,
or if you have the gem system installed :
gem install rools
and use it from within your ruby code
require "rubygems" require "rools" #...
If you want it fresh from the source, check out the source by running
svn checkout svn://rubyforge.org/var/svn/rools
and then run
to build the latest gem with the latest source.
You can run the unit tests with
(more about unit tests in the devdoc)