How do you watermark a picture?
Do you have any editing software that came with your digital camera? Those programs usually have a watermarking feature of some sort.
I am not too sure what programs you may have available to help you.
If you google watermark images, you will find loads of information, some using online software, and some tutorials which will help if you use programs like Photoshop etc.
I do it in photoshop and put my eBay user ID REALLY BIG across the entire picture, but as an overlay, so it is there, but you can barely see it.
And I make note that my pictures ARE watermarked and that is what you are seeing on them LOL
I use paint sometimes to do the same thing as ^^^^^ and every computer has paint on it automatically