As User with publisher rights you can upload photos to our gallery.
1) Downsize photos at your computer (not larger than 1080px at lenght or height)
2) LogIn at frontend
3) Follow instructions http://www.balbooa.com/joomla-gallery-documentation/front-end-management
-> Go to a gallary and add new category
and then upload photos and select a album photo
Watermark will be added automatically