Sims 3 is a role playing game that allows you to create characters and guide them throughout their lives. There are certain features in the game that are not regularly available however. Some of these features include the ability to unlock hidden traits or special skills, or to allow certain challenges to be triggered more often. These features can become unlocked by installing a game modification, or mod for short.
Find a mod you want to install in Sims 3. There are many websites that offer free mods, such as modthesims.info or peggyzone.com. When you find the mod you want, click the "Download" button and save it to your computer desktop.
Wait for the mod to download. Extract the file. This can be done by right-clicking the file and selecting "Extract Here."
Open "My Computer," then "Disk: C." Locate and open "Program Files" from the list, then "Electronic Arts." Inside this folder will be a Sims 3 folder. Double-click on it.
Click the "Mods" folder inside of the Sims 3 folder. If there isn't a folder named "Mods," create one by right-clicking and selecting "Create New File."
Download the file "Resource.cfg" from the link in Resources. Place this file in the "Mods" folder that you just created.
Drag the mod from your desktop into the "Mods" folder. Start Sims 3 and the mod will now be installed in the game.