You can add the new credit card by logging in to your BuddyBoss account and clicking on the Billing tab. On the next page, click Add Payment Method and enter the Credit Card, Expiry date, and CVC code. Save the changes made by clicking on the "Add Payment Method" button. Once done, it will go to the page where it shows the 2 credit card information. Click the icon "Make default" to make the new credit card the default credit card. 

You can refer to the image below: