simple captcha instllation problems

I have installed SimpleCaptcha plugin to vendor/plugin

For the setup the plugin I am getting

rake simple_captcha:setup

Gives me error: rake aborted!
Don't know how to build task 'simple_captcha:setup'

I checked rails version by

gem list

rails (3.0.7)
railties (3.0.7)
rake (0.9.0, 0.8.7)
rake-compiler (0.7.8)
rmagick (2.13.1)
rubygems-update (1.8.3)

ruby -v

ruby 1.9.2p180 (2011-02-18 revision 30909) [i686-linux]

I am looking for help on this.