Hi Max.
If you want a signature on your photographs you would place the signature on each image using a program such as Photoshop.
The signature must be small and no block letters - or it will not print.
NOTE: watermarks and signatures on your images can deter sales - A signature on a painting is normal - but sales can suffer with a signature on a photograph. Unless you happen to be the number one most famous photographer in the world. Then a signature may help sales.