Not able to add my credit card

See this link for help with that --> If you can't add a card to Apple Wallet to use with Apple Pay - Apple Support

The most common reasons a card can't be added is the issuer of the card hasn't approved the card to be used with Apple Pay. Or the country one lives in hasn't approved Apple Wallet. Or the card is issued in a different region/country than the country you live and use your iPhone.