1) Go to your User Control Panal.
2) Click on "Edit Signature" on the left side of the page
3) Your signature text box should appear. Click on the image icon over the text screen (it should read "Insert Image" if you hold your mouse over the yellow image icon).
4) A box should pop up that says "Enter the text to be formatted". Add your url in that text box, click "OK".
5) Click on the "Save Signature" under the text box.
Your signature picture should appear once you've done all this. If it doesn't, drop a PM to Joe Gardner so he can check and see if there's a problem with your account.