While exposing your photos to the public view you might want to protect your work by adding watermark to photos. Note, that this functionality is available only for Premium users.
To add watermark to your photos, log in and go to 'Settings'.
Now choose 'Site settings' and scroll down a little bit to see headline 'Add watermark to your photos'. Enable that option and from now all your new photos that you upload will be displayed with watermark.