What is the easiest way to convert a jpeg into a watermark with CC 2014?

What is the easiest way to convert a jpeg into a watermark with CC 2014?
I signed a paper and uploaded the image to the computer as a jpeg to be turned into a watermark.  I'd done it before for a different kind of photography, but have not done it in so long that I cannot remember the steps nor can I find the tutorial video I had watched that taught me how to do it.
Any help would be greatly appreciated