Your camera opens on the next screen.
Nothing is recorded, saved or sent anywhere.
On a computer this works by holding the painting up to your webcam. For the real thing, open this page on your phone:
This takes a few seconds the first time. After that it works even with no signal.
This app needs the camera, and the browser built into this app doesn't allow that.
Tap the … or share button at the edge of the screen, then choose Open in browser (Safari or Chrome).