I've searched internet for Amiga Arabic language and all I found is the Arabic font here: http://aminet.net/package/text/font/HebrewArabic
Install it to AmiKit:Fonts folder and then run AmiKit:Prefs/Fonts program and configure it to use the new font.
In order to use the font correctly, you have to get yourself the appropriate keymap file, this will remap the keys on the keyboard to the appropriate letters of the foreign alphabet. However I did not find such a keymap myself. If you manage to find it, copy it to AmiKit:Locale/Flags/Keymaps and activate it using AmiKit:Prefs/Input program.
Also it would be nice to have the programs localized in Arabic language. For this you need to set the Locale environment to Arabic using the AmiKit:Prefs/Locale program. For this to work, arabic.language file has to be installed in AmiKit:Locale/Languages folder and arabic.country in AmiKit:Locale/Countries folder. And also the translated text (catalogs) of the programs too: in AmiKit:Locale/Catalogs/Arabic folder.
However I did not find the files myself, maybe you will have more luck. Usually all the files I mentioned are located in one package, similarly to the locale archives here: http://os.amigaworld.de/index.php?lang=en&page=12