uploading google photos to marketplace

So is it me or am I totally missing it. I take pictures with my phone. It saves to google pictures. I go to marketplace, (Same with craig lists, offer up, or other local selling platforms.) On the final step to add photos It just does not let me select the google platform photos. I cannot seem to select direct from photos. Unless I download them to my PC and then select my downloads. Seems like a lot of extra steps and way too much effort.

It puzzles me because the opposite happens on the phone. Easily allows to select and upload to another site.

What's the easiest way to do this process