Need to change my charge card number on method of payment

As you must have missed the Apple Recommended post on this page, here is what it said:

Add a valid payment method. Then remove the other(s).

Change, add, or remove Apple ID payment methods - Apple Support

Add a valid payment method. Then remove the other(s).

Change, add, or remove Apple ID payment methods - Apple Support

I need to update my new credit card Number. i can't seem to get into form to delete my old credit card and add my new credit card number. Why do you make so hard to do this task.

[Personal Information Edited by Moderator]