If you are using a Mac with the software Photos (previously named iPhoto) you can not drag images directly from the software to your web browser for uploading into your product. You instead first need to export the images from Photos to Finder. The easiest way to do it is to select all photos you want to use and then drag them from Photos to a Finder window. It can take a few seconds to a minute before it is done depending on how many images you wanted to export. Once you have them in Finder you can easily upload them to your photo product like any other photo.