Hosting ruby on rails on Bluehost- installation of specific versions of ruby, rails

Hosting ruby on rails on Bluehost- installation of specific versions of
ruby, rails

I have logged into my Bluehost server through SSH and I am looking to
install ruby v1.9.3 and rails v3.2.13. The version of ruby by default
seems to be 1.8.7 and the rails 2.3.11.
I tried to upgrade rails using the following command in the terminal under
the SSH session:
gem install rails -v 3.2.13 --no-rdoc --no-ri
I get the following output:
Successfully installed rails-3.2.13
1 gem installed
I then tried running a check that it was installed:
rails -v
I get the following output:
Rails 2.3.11
Why does it not get upgraded? Additionally, what command should I be using
within bluehost SSH session to upgrade ruby?