How to install .gem files in Ubuntu 9.04

Hi, I am new to rails . i am trying to install gems from the source . I
AM HAVING ClothRed-0.4.1.gem file . How can i install this gem manually
. This .gem file had data.tar.gz and metadata.gz file

why arent you installing with apt-get?

sudo apt-get install build-essential libopenssl-ruby ruby rubygems
ruby1.9.2-dev libsqlite3-dev

gem install rails