I need help to update my VISA card details to pay for my subscriptions. HELP step by step talk through to complete the transaction. Brian Sutherland.

I have been trying to update my Visa Card details for Scotlands Gardens and Landscapes AND Games old and New. I cannot fathom how to do this. I did receive help previously and was promised an email giving me step by step instructions. I have not received this emal. I WANT TO PAY but need help to complete the transaction.
Brian SutherlandScotlands Gardens and Landscapes.
also for Annie Sutherland Games Old and new.
HELP PLEASE.