Launch it, and the login screen will appear on the startup screen. Click on the three dots to the right.
Select App in the Air for Business here.
Or, in case you missed the login page when starting the app, open the Profile – Settings in the app.
Select the Business account from the list.
Here you can use your Business email and password.
That's all. In the booking section at the top left, click on Personal booking, and switch to Business booking.
Your reservations will now be for business only (you can always switch to Personal booking for your reservations).
NOTE: If you already have the app, the current account does not go anywhere. A business login (App in the Air for Business)is an additional authorization method that exposes all the app's business functions (including travel policy for flights and corporate card payment).