At the top of “my photos” is a little button that says “select”, you click that and then you select whatever pictures(use ctrl to select more then one), then at the bottom of the page you “add to collection/shoot”. When you’re done click “select” again to return back to the normal page.
I had the same question when I first started!
Right now, even if I only have two pictures from a shoot I will add them to “a shoot”. If someone looks at my picture, below it will be the variations-but only if it’s part of a shoot.
I’ve had to learn a lot in my first months. It will get easier!