All your active credit cards goes here. Adding credit card doesn't mean you are linking your actual credit card with Spendwise. This is just a way to track your credit debts.
Opening Amount Owed is the amount you owe in your credit card. This is for Spendwise to know how much debts you owe.
You can have multiple credit cards. Current Balance shows the total amount owed (this includes the transactions you make using a credit card).
Best way to knock down your credit debts is to have a clear picture of how much you owe to credit companies.