You need the Unleashed Expansion Pack to use Animal Skins.

Choosing and downloading your skins is now quicker and easier than ever! You can download individual skins by clicking download now. Batch downloads are also available for subscription members. Clicking the download selected button will put together a zip file containing all textures on that page with a tick in the select box. It couldn't be easier!

You will need WinZip. You can download a trial version from here.

To use custom made Sim Skins and Animal Skins in the game, download the ZIP file for the skin(s) you choose. Unzip the files into the \Maxis\The Sims\GameData\Skins directory as shown below.

Once you have imported them into The Sims, you can find them on the Create A Sim screen next time you start the game (Adopt Pet screen for animals with Unleashed users). Alternatively, if you want to mix and match bodies with heads, use SimShow. This program has a detailed (read me.doc) document enclosed explaining how to do just that. When you have selected the Head and Body that you want to put into the game, click on the "import into game" button.

Remember, if you created an Adult Dark-Skinned Male, you must select this category on the Create A Sim screen to view your custom skin.

If you would like to learn more about editing skins, please see the Tutorial. You could also make use of the Editing Forum to help you on your way.