I can't see language list in I18N/L10N preferences in " Home › Administration › System Preferences › Modify system preference 'language' ". only language I can see is English, I want to add Arabic or Persian to this list for changing the language of Opac and Intranet to Arabic. how should I do this ? and which configuration should I do ?

It means that your Koha installation hasn't Arabic templates. Ask you system administrator to install them. He has to find a directory named 'misc/translator' and run this script: ./install-code ar-Arab -- Frédéric DEMIANS