In order to deposit log in to the app, tap on "Top up" (the "+" sign), enter the amount that you want to deposit and confirm it by clicking on "+".
The app will display the available top-up methods for your country.
Bear in mind that when depositing with a credit/debit card you must select if the funds will be used for "gaming" or "non-gaming".
If you intend to use the funds for gaming make sure to select that the funds are for "gaming".