Before you can add a SIG, you must first find an image hosting site to store your image file.  A couple popular ones are http://photobucket.com and http://imageshack.com.

Important - Preferrably SIGs should be no bigger than 400 W x 130 H or the equivalent to 52,000 pixels or less.  If your image is too large, you will be asked to reduce its size; as per the forum rules.

To add a SIG, follow the steps below:

1.  Click the "Edit Profile" link in the top right corner of the Dallas Cowboys Fan Zone
2.  On the "Signature and Bio" tab, click in the Signature text box
3.  Type [ IMG ]path to image file[ /IMG ] - There should be no spaces between the brackets and the IMG tags.
4.  Click the Save button and wait for the message stating your profile has been successfully updated

Remember that you first need to find an image hosting site.  Do not copy and paste the example above, it's only an example.

Good luck.