You may edit a card's name through the "My Accounts" drop down menu.
Step by Step:
- Go to "Money" and tap on the top left arrow to open "My Accounts".
- Locate the card you would like to rename and tap on the arrow to the right of the card.
- Tap on "Rename Account".
- Type in a new card name.
- Tap on "Rename" to confirm the change.