If the card is connected to a card profile that is on the Ladder:
1) Click on the card in your Collection.
2) On the top right, click on the bookmark icon with the minus sign on the top right.
3) A dialogue box will open asking you to confirm that you are sure you would like to delete the card from your Collection.
4) Click OK button to confirm. The card has now been removed.
If the card is private (manually added and NOT connected to a card profile that is on the Ladder):
1) Click on the card in your Collection.
2) On the top right, click on the trash icon on the top right.
3) A dialogue box will open asking you to confirm that you are sure you would like to delete the card from your Collection.
4) Click OK button to confirm. The card has now been removed.