In the top right corner of the home screen, click on your user profile photo to go to the More page, where you will find our settings and information menus.
Here you will find the Settings menu and within that the Bank Cards menu.
You can add more credit cards by clicking on the "+" button at the bottom of the page. You can also name the card by tapping on "My card" in the card list.
You can tell us which one is the default by the asterisk next to the card.