Hi there, Are you logged into the app? You should see a button on every photo that says add to ideabook. Just tap there to save it.

I'm looking at the iPad app, and the "Add to Ideabook" option is at the bottom of the screen.
I tapped photos, chose a photo, tapped it to open it to full screen.

This is the app with someone NOT logged in. I don't know how/if it changes if you are logged in.
Try opening a photo completely. If you don't see the option, tap the photo once or tap with two fingers to see if some sort of menu pops up.

Thanks so much :)