^ I don't know about the app, but I know that on the website you have to log in and then go to the main page. You click the album there, and then you can enter the code
Edit: I tried the Android app. Not sure if it's the same on iPhone but I have to click the home button on the bottom (the one on the left, with a house) and choose the album there, then it redirects me to the website, I have to log in and then I can enter the code