Hi Alexa, I ran into the problem of installing the Arabic language pack as well.
I'm guessing you've moved on, but if not, and for others, here's what worked for me.
You need to install it through the command line, which is covered in these instructions:
http://ka-lite.readthedocs.io/en/0.16.x/faq.html#how-can-i-install-a-language-pack-without-a-reliable-internet-connection
Major note: I believe that the reason the language pack isn't available to install through the Admin pages is that it is only 22% translated. This amount is contrary to what the KA Lite's language dashboard states (99%), but that must be a bug.
https://hub.learningequality.org/languages/dashboard
There are some major translation issues with the course menu when using the Arabic language pack. I'm seeing items in Arabic, but also in Chinese, Cyrillic, English, and Dutch (I think).
Hopefully some translations are better nothing.
Cheers,
Ben