Nidan, this is so easy that even a Cowboys fan can do it. In fact, I think you PM'ed me in August asking the same thing.
1) Click on the "User CP link" in the upper left of the secondary menu on top.
2) Navigate down to "Edit signature" - about 1/2 way down the left hand menu.
3) Type the Text for your link - e.g. "Arizona Cardinals Website" Then using your mouse, highlight the text.
4) Click on the globe with a chain link on top in the icon menu - second row under the happy-face smilie dropdown.
5) In the popup, enter the http:// URL and bingo! Save signature and you are good to go.
LOL, I am so tempted to put a hyperlink to McCain/Palin in your sig just to get you moving on this, but I thought better.