Go to the DKPsigs.com website and follow the instructions to create you sig. When you get to:

Then go to the guild website and click on the "Characters/Settings" link at the top of the page - you must be logged in for that. That will open:

That will display your signature editing area, click on the button shown:
Paste the link from the DKPSigs website into the box as shown:
Your sig should now be shwoing in the signature editing area, click "Save Preferences":
Hopefully you now have a sig!!