When I want to upload images I first move my image or images to a new folder and name it something like National Gardening Association. I then give each of the images (if there are more than one) a number and a name. Something simple like 1-Dandelion.
After that, I am ready to follow the prompts just as you have already tried, but this time I know to click on that one folder to open it, then select only one image and click to open it. Wait a moment or three and the image should load. I do not resize my images as NGA does that for me so my larger images take just a bit longer to load. I don't mind waiting.
Good luck and keep trying. It does get easier.