Go to your dashboard. https://vipclubcontest.com/contests

Hover "Account" and select "Profile" from the dropdown menu.
​https://vipclubcontest.com/profile

Go to Billing section.
​https://vipclubcontest.com/profile#billing

Scroll down, enter new credit card info into the "Update your Credit Card" section. 

Select "Use This Credit Card" button.