installing ckeditor - problem

I am trying to install ckeditor.

I downloaded the software under public/javascripts/ckeditor.

in the console  I ran:

ruby script/plugin install git://github.com/standout/rails-ckeditor.git

Then I am trying to run: rake ckeditor:install

and I get the error: "don't know how to build task ckeditor:install"

What should I do?