How to add credit card to wallet

The page linked above, and which you may have visited before composing your question, has a link to Set up Apple Pay - Apple Support

The Set up Apple Pay page has the instructions you need to add a credit card to Wallet.

Before you attempt this however, check that Apple Pay is active in your country. See Countries and regions that support Apple Pay.

just a slight adjustment - not only the country needs to be supported but also card issuer. Not all issuers/banks offer this Apple Pay compatibility to their clients, even if the service is available in the country.

Quite so, and links to participating banks etc. are adjacent to the list of countries in which Apple Pay is active.