When you are on your "My Cards" page, click on the card you want to add the funds to. It doesn't really look clickable, but click on the card image and it will take you to another page where there is the option to transfer funds to that card.
When you are on your "My Cards" page, click on the card you want to add the funds to. It doesn't really look clickable, but click on the card image and it will take you to another page where there is the option to transfer funds to that card.