First, you need the Linux version of the RAR archiver download that at
http://www.rarlab.com/download.htm it's a command line only tool. Too install it, after extracting the install files, open a terminal windows, and change to the directory the files were extracted to (Example: cd /tmp/rar_install)
gain root user access with the su command and issue the command make
to extract the file
unrar e /(full path to archive)/(archive name)
That is a basic method, to see all option use the command:
unrar --help
And to create a rar archive:
rar --help
Hope that helps......