unable to interchange ruby versions using RVM

hi everyone i've installed RVM in ubuntu 11.04 which use this command
"use rvm 1.9.3" it is showing this thing
"No command 'use' found, did you mean:
Command 'nse' from package 'ns2' (universe)
Command 'muse' from package 'muse' (universe)
Command 'uae' from package 'uae' (multiverse)
use: command not found
"

and when i type rvm list it is showing below list
rvm rubies

   ruby-1.8.7-p358 [ i686 ]
   ruby-1.9.3-p125 [ i686 ]

# Default ruby not set. Try 'rvm alias create default <ruby>'.

# => - current
# =* - current && default
# * - default
what is the problem

thanks in advance

hi everyone i've installed RVM in ubuntu 11.04 which use this command
"use rvm 1.9.3" it is showing this thing

Is that a typo? It's supposed to be:

rvm use 1.9.3

-philip