How to add a card to make purchases

If you are talking about purchases from App Store and/or iTunes Store:

Change or remove your Apple ID payment information - Apple Support

If you're referring to Apple Pay:

Using Apple Pay in stores, within apps, and on the web - Apple Support

or

Set up Apple Pay - Apple Support

Regards

Giulio

Hi

Go to iTunes main page bottom of page apple I'd click that view I'd Go to manage payments to add a credit card.

Cheers

Brian 🇬-1F1E7;