Mac App Store Installation Mods
 

If I buy the game through the App Store on Mac, will I be able to modify files? thinking about adding logos and/or stadiums. also the all in one mod.

Is the process for installing mods posted somewhere?

or will i need to buy it from OOTP to be able to mod?

It is the same as in other versions (except Steam), you have the Add-Ons central. Check the mods section of the forum for info on how to get it working properly.