You can upload your sig by going into your profile settings. Once in your profile on the left hand side you should see edit my signature. this is where you will upload the signature. Afterwards if you want to add credit for the sig you can add a line of text using the post editor below your sig like i have done on my signature.
But please limit the amount of the text to a minimum in this area for anyone wanting to add additional text info to their sigs it not an area to start a blog
We do reserve the right to edit or shorten these additions to the sig if they are overly done or offensive