Font release note B NazaninBoldBorna Nazanin BoldB Nazanin BoldVersion 2.01 - Build 1379BNazaninBoldParsa 2001 - Borna Rayaneh Tags: B Nazanin, Arabic, BNaznnBd.ttf, Windows font. Farsi font free download - Farsi Keyboard, Farsi Keyboard, Farsi Keyboard, and many more programs.
Mac OS X comes with three different Persian keyboards. Enable them all, try them out, see which one you prefer. (You can also install a different one, if you choose.) Then use the Geeza Pro font to begin with.
There are quite a few other resources, which you can find by googling. I suggest a closer look at Mellel
<http://www.redlers.com>
It's an excellent Mac word processor; moreover, it was designed specifically for RTL languages.
I also suggest checking the Iranian Mac User Forum, where you are likely to find more specific advice