Problem installing plugin

Hi I am having ruby 1.9.1 version . I am trying to install
acts_as_taggable_redux plugin for tagging. When i do the following
command :

ruby script/plugin install

Its says

already installed: acts_as_taggable_redux
(GitHub - geemus/acts_as_taggable_redux: Allows user owned tags for multiple classes, and makes tags easier to work with.). pass --force to

when i try doing ruby script/plugin list . Nothings returns…

rails version i am using is 2.3.1

i assume its not installed as i search for tag_cloud ruby file and not
able to find it.
what is the problem?