# Install language-pack-ar and language-pack-ar-base. These packages is used to translation for Arabic language
sudo apt-get install language-pack-ar language-pack-ar-base# Install ttf-arabeyes for Arabic fonts and libfribidi0 for Arabic Unicode algorithm
sudo apt-get install ttf-arabeyes libfribidi0# Don't forget language-support-ar package
sudo apt-get install language-support-ar# Then go to System*Preferences*Keyboard. There are some tabs, choose Layout
# Click Add button and you will get a dialox box contains two tabs: By Country and By Language. Choose By Language then Arabic for Language and Arabic for Variants.
# Click Add button once more and you will see this icon in your main panel in desktop:
# Click USA and it will be switched to Ara and vice versa.
I get this how-to here. Enjoy!