Download your desired mods listed in the left side menu, extract the (.package) files from the (.rar or.
3.3- Unpack the file to your Documents\Electronic Arts\The Sims 3\Mods folder.
3.2- Download / save the new Resource.cfg file located at this link.
3.1- Hit your back button and go back to the Mods folder so you are on the same level.
Note: This file is needed to add references within the game, where it can find mods (*.packages) on your system, without this file the game will ignore any additional mods (*.package) you have installed.
Without this instruction all mods (*.package) go in the Packages folder.
Note: The Overrides folder is only to be used when a developer asks you to place his/her mod in there.
2.4- Create another sub-folder within the Mods folder and name it Overrides (watch the case it must be exact).
2.3- Create a sub-folder within the Mods folder and name it Packages (watch the case it must be exact).
2.2- Click to open the Mods folder so you are inside it.
2.1- Create a folder and name it Mods (watch the case it must be exact).
Note: Just remember that in Windows 7 Documents is under Libraries, Windows Vista is under Documents and Windows XP is under My Documents.
Go to C:\Users\\Documents\Electronic Arts\The Sims 3.
You cannot do this while your game is running as these files are in use, so shut the game down first.
Quick and Dirty version for installing CC and Mods.
You can find those files by using the Pages and Files link on the left-hand side.
Earlier versions of the mod may be available on the site, even if they are not linked to the download page.
Doing so will have unpredictable effects on your game.
Either unzip (extract) directly or move the package file to your Mods\ Packages folder within (OS Win:) Documents\ Electronic Arts\ The Sims 3 directory and overwrite any older copy of the mod you have installed.
Note: By default, Windows will open zip files just like file folders, displaying the contents directly in the explorer window. In Windows, this can be performed by right-clicking on the file and using the Open With.
Find the file on your HDD and unzip (extract) the content from the file.
Note: With your Internet Browser you're able to open the zip file directly and extract the content on your HDD by doing so you can skip step 4.
At the bottom of the mod's download page will be a download link for the zip file containing the mod.
See Patch Level Compatibility for details.
Next, click on the appropriate Phase for your Patch-Level.
Locate the mod's download page, by clicking on the appropriate mod link on the left-hand side.