I think the problems is that you're going to the applications folder.
If I want to upload a picture from Photos to google images, for example, I click "upload" and I get a Finder window. I would then use the sidebar on the left side, go to the bottom and find Photos, and it will show all the pictures in the Photos Library

I'd use the search window to find the one I want, my aunt, maybe, and it would show pictures of a bunch of aunts, and I could pick the one I want.
It's a good idea, by the way, to give the picture you want a helpful keyword so that you have something to search for to narrow the choices.
Oops, I see that Yer_Man and I had the same idea. I happen from time to time...