This is why Apple have hidden it from Lion onwards. You can render Applications useless and potentially screw up the OS by deleting the wrong things.
Please note that the Preferences folder has really important files in it so make sure you don’t delete ANYTHING apart from the files mentioned below. In order to make sure you have a completely clean uninstall of the game, follow the steps below. A lot of Preference files are left behind when you uninstall The Sims 3 using the Uninstaller in the Applications folder. Even then it’s not 100% guaranteed that your game will work again after reinstalling but it should give it the best chance possible. If you’re having problems with your game this is a last resort but it will only work if you really get rid of everything. These instructions are to completely delete everything Sims related from your Mac – CC/Mods/Saves/Downloads, everything (to manually uninstall a single EP/SP please read this guide). For the 64-bit version uninstall through Origin Applicable only to the 32-bit version of the Sims 3.
