If you wish to save the progress in the app, you should link your account to Facebook/Email.
The log-in options may appear during the onboarding process and on the Profile page.
Unfortunately, on Android devices, the only option to log in is using a Facebook account.
In order to proceed with the login, please, follow the instructions:
1. On the onboarding process, click on the "Maybe later" button.
2. Go to the Profile Page located at the low-right corner of the screen. You will notice only the Facebook option to log in.
3. To do so press on the "Facebook" button, choose the account you would like to connect and you are ready to go.