When you click select image, you can upload or select an image from media library, that is going to be used as a watermark image. Then during image upload in selected posts/pages/media library (depending on your setup) the previously chosen watermark will be automatically applied.
If you enable manual watermarking you’ll see new option under Bulk action in Media library, which allows you to watermark previously uploaded images.
How to Get Support
After you register and login to the site, you may post all plugin support questions in the Support Forum.
If you need to provide private info, please create a ticket and then reply to it using Set as private reply option.