Press the plus sign after selecting a person. A new screen with some input fields will open. You can type in the name or select a name of a contact. Then you can choose a description and an amount.

You can also change the date and then you have to select if this person owes you the amount or you owe the amount to the person. If you want to get a notification you can also select one of the 4 notification types. Make sure that you activated the notification in the app settings and generally allowed the app to display notifications.

You can change the currency of the debt by pressing the currency symbol next to the amount.