Things You'll Need
Instructions
Download a "Sims 3" celebrity mod. Hundreds are available on repositories such as "Mod the Sims" and "The Sims Resource." Both are free to use, though "The Sims Resource" does require that you register.
Unzip the mod. Macs have a built-in unzipping functionality -- simply double-click the file to unzip it to the current directory. On Windows PCs, you can download and install a free program to do the job, such as "7-Zip" or "WinRar." Once the software is installed, right-click the mod and choose "Extract." This will place the celebrity Sims folder(s) and the associated files in your documents folder.
Navigate to "The Sims 3" override directory. By default, it's located at "\Documents\Electronic Arts\The Sims 3." On Windows PCs, you can readily access it by opening "Documents," or "My Documents." On Macs, you can get to "Documents" by opening "Finder" and then clicking on "Places."
Return to your celebrity mod files. If they're in a folder, open the folder. You're looking for files that end with ".Sims" and ".Sims3Pack."
Drag and drop files ending with ".Sims" into your override directory. These automatically install into your game.
Double-click files that end with ".Sims3Pack" and then click "Install."
Activate "The Sims 3" game and select "Create a Sim." Browse through the presets until you find the celebrity you just installed.