Tools/Other Essentials Needed

Before you can install custom content into your Sims 3 game.

*Remember Windows and Mac users have different things to do or places to go to within their computer, SO READ CAREFULLY!*

-You need Sims3 Framework, which does something to your game to make custom content outside EA to work.
For Windows users, you can get that tool here - http://modthesims.info/download.php?t=384014
For Mac users, you can get that tool here - http://www.modthesims.info/download.php?t=349349

-You need a extractor tool called WinRAR, because people who make custom content often compress it, so the file will be smaller, all in one place if it's multiple files, and easier to download, and the file will have to be extracted and the file(s) extracted is(are) the actual custom content files for the game. When you install this tool, it will be trial, but don't worry, you can still use the tool for this purpose, even after it expires, you'll just get an annoying pop-up about buying it, but it will still work. You can get this tool here - http://www.rarlab.com/

-Making a Folder called Packages, this is a folder that your Sims 3 game can recognize for custom content to be used in-game.
If you game is older than Patch 1.12, then for Windows 32-bit user, look in directory "Program Files\Electronic Arts\The Sims 3\Mods", for 64-bit Windows users, look in directory "Program Files(x86)\Electronic Arts\The Sims 3\Mods", or if you are using a Mac, look in directory "Contents\Resources\transgaming\c_drive\Program Files\Electronic Arts\The Sims 3\Mods", check for a folder called Packages, if none there, then make one called Packages. If you have any Stuff Pack or Expansion Pack, the you need to make this folder in the directory of whatever one you have installed, in "Program Files\Electronic Arts\(The name of the SP or EP you have installed)\Mods" or "Program Files(x86)\Electronic Arts\(The name of the SP or EP you have installed)\Mods" or "Contents\Resources\transgaming\c_drive\Program Files\Electronic Arts\(The name of the SP or EP you have installed)\Mods".
If your game Patch is 1.12 or newer, then for Windows XP users, look in directory "My Documents\Electronic Arts\The Sims 3\Mods", for Windows Vista or Newer OS and Mac users, look in directory "Documents\Electronic Arts\The Sims 3\Mods", check for a folder called Packages, if none there, then make one called Packages. If you have any Stuff Pack or Expansion Pack, the you need to make this folder in the directory of whatever one you have installed, in "My Documents\Electronic Arts\(The name of the SP or EP you have installed)\Mods" or "Documents\Electronic Arts\(The name of the SP or EP you have installed)\Mods".

Lots of information, but I want to make sure that I got everyone covered :)

I also hope that this helped you :)