You can remove the card you no longer want by going to the relevant card in the app and then:
Tap the (i) next to the card
Click on Edit in the top right hand corner.
Click on Remove card from Curve at the bottom of the screen.
In Curve 2.0 you can also remove a card by holding down on its image in the grid view (tap the button on the top right of the home screen to switch between the carousel and grid) and tapping the 'x'