I will say - make sure you've installed the Mods folder here:
/Users/<username>/Documents/Electronic Arts/The Sims 3/
Not in the Electronic Arts/The Sims 3 folder by itself. The above address is where the game also stores save games, etc.
If you only see folders that say Caches, Game, GameData, Support and Thumbnails, you're in the wrong place.
If you're in the right place you'll see folders like Collections, ContentPatch, Custome Music, DCBackup, DCCache, etc.
So make sure you've set up your Mods folder in the right place.