Adding Additional Fields at Checkout

Is there a way to add an additional field at checkout? We'd like to add Type of Credit Card with the choices being American Express, Mastercard, Discover, or Visa.

On another topic this was suggested: You can add additional fields on the credit card form by editing the file "payment" of the view "checkout" via the menu Display->Views. Then, you will have to modify you payment plugin to use that field.

Our developer doesn't understand how this can be done without more information than the statement above.

Thanks!