In the Documents/Electronic Arts/The Sims 3 folder, create a new folder and name it Mods. If you don't have that folder yet, follow the instructions below. Place the package files into Documents/Electronic Arts/The Sims 3/Mods/Packages. In the game you recognize the custom content by the shopping bag. Remember to uninstall an item first before you reinstall it.
Select the items you want to have in your game and click Install. Start the Game Launcher and go to the Downloads tab. If you downloaded ZIPs, you first need to extract the Sims3Packs from them, then place it in the Downloads folder.
If you have downloaded a lot of Sims3Packs, place them into: Documents/Electronic Arts/The Sims 3/Downloads. Double-click the Sims3Pack you have downloaded and it will install into the game.
