In the neighbourhood screen in the game, click on the Import button to import the family into the game.
The Sims File Cop cleans your The Sims folders for files that are known to crash your game that you may have downloaded to your system.
It will check for each file type and report if it found any and how many it removed.
It will also move any bitmap textures that are not 256 color to the BadTextures folder. The BadTexture folder can be found in the folder that you installed File Cop to ( usually c:\Program Files\Maxis\The Sims File Cop ). You can open these in any paint program and convert them to 256 color ( which may be called 8-bit, or palletized 8-bit by the paint program ) and save them back to the GameData\Skins folder if you want to repair them. You may also simply delete them.
Other bad files will be moved to the BadOtherFiles folder.
Temporary files left by using The Sims Exchange will be deleted.
I personally have found this program to be invaluable after downloading. Using this program immeadiatley after installing anything new into your game is a good habit to get into.