First thing you do is upload your animated email signature to your web-hosting provider.  You can also use any free picture-hosting website, like http://www.photobucket.com, http://www.imageshack.us, or http://www.pictiger.com.  It is important to take note of the URL (website address) of the image you uploaded to your preferred picture-hosting website.  Example of which would look something like this -> http://www.photobucket.com/your-signature-filename.gif