When at the login screen, press the button Login Online. Note that tapping Switch to regular login will take you to the normal login screen.
Microsoft’s authentication portal will open. Enter your credentials or choose your user from the list of previously used ones and click Sign in.
If you haven’t previously created an offline passcode, you will be asked to do so directly after logging in. You may skip this step and it will come back the next time you log in.
Either enter a 6-digit passcode and click Save or click Skip to log in to the app.
When at the login screen, press the Login Offline button.
Enter your username and the 6-digit passcode and click Login. Normally the username will be set to the last logged in user to make this process easier.
If the correct username and passcode combination was entered, you should now be logged in.