This FAQ topic applies to all version 3 Photostore sites and version 4.
To create a watermark:
A watermark file needs to be a 2 layer png file. The background layer needs to be 100% transparent. The foreground layer can be anywhere from 20 to 30% opacity. If you wish for a more visible watermark you can raise the opacity to around 40 or more, but it will get real "strong" at that level. The foreground seems to work best if the text or graphics is white.
(version 4.3 or older)
To add a watermark to version 4 upload the png file you have created to the assets/watermarks/ directory of our store. To change your store to use that new watermark just log into your store manager and go to the settings -> look & feel area and then click on thumbs, previews, or rollovers and select a watermark from the drop down box setting.
To add a watermark to the store log into your manager and go to settings -> look & feel -> watermarks tab area. From there you can upload and delete watermarks.