The easiest way to add some form of copyright to your image is to use the text tool in any photo-editing program (heck, even Microsoft Paint will do the job) and tag your name on it. You can do it discreetly by writing it in a corner, in small font size, or you can plaster it over the entire photo. Draw a box around it, color it, use a funky font - it's entirely up to you. This method might not be attractive, but it's the fastest and easiest way to add a watermark. If you're sending out a set of proofs for a client to select which images they want printed, something like this might be sufficient. For a cleaner approach, read on.