I perused these forums in the hopes that someone would detail a way to mod Fate for the macintosh version of the game. Having recently been forced to switch from windows to macintosh, I was woefully unaware of where even to begin to find the necessary .dat files described in the other, pc-aimed tutorials. Unfortunately, I found posts that were less than helpful. Thus, I began an expedition to find the answer myself. This is a description of that adventure and how I discovered the way to do it. I hope that it is pedantic enough that even the most inexperienced mac user, like myself, can replicate my success.
1.) First I had to figure out how to reveal hidden files. That's right, macintosh's have files that are normally kept out of sight because they are not technically supposed to be tampered with. However, the files we are looking for turn out to be hidden. To make files no longer hidden, I found a useful guide at:
http://guides.macrumors.com/Viewing_hidden_files_on_a_Mac
This will not only tell you how to reveal hidden files, but also how to hide them again.
2.) After revealing the hidden files, you then have to actually find the files. To do this, go to the fate folder in the Applications folder (Located at /Applications/Fate/). Then hold control and click on FATE.app. A menu should appear. Click on "Show Package Contents". This should bring you to a folder with a folder called "contents". Inside that folder, open a folder called "Resources". Then, there should be a folder that looks lighter than traditional folders called ".Game". Inside that folder, open the folder "Fate Data". This folder contains all of the files that are talked about in the other tutorials. In the end, the folder you should be in inside the FATE.app file is:
/Contents/Resources/.Game/Fate Data
If you do not see the folder ".Game", then you have not successfully revealed the hidden files. Therefore, you should go back to step 1 until you can find it.
3.) Now that you know where the files are, you can effectively mod using the other tutorials that already exist for the PC.
I hope this post helps.