The PIN for the new card (a physical or virtual one) should be set when ordering it.
The PIN code is set after choosing the type of the card, and filling in the delivery address (if it is the physical card). You will be asked to enter the PIN twice to confirm and avoid mistakes.
The created PIN code can be conveniently displayed later on in the card details, by clicking on the card icon SETTINGS (two lines located in the top-right place on the screen ) so don't worry if you forget it.
The PIN for the physical card can be changed in the ATM, not in the app.