To use Piano Sphere, you need a Roland Account (free). Start the app and follow the on-screen instructions, and you will see a screen like the one shown below, asking you to enter an email address.
Enter an email address that you can use for your Roland Account (if you already have an account, enter the email address you registered). Then tap CONTINUE. A Verification Code will be sent to the email address you entered.
Note: If you already have a Roland Account and prefer to sign in with a password, you can tap "Prefer to use a password? Sign in here" instead.