Download the "Google Pay" app on your smartphone. Open the app and tap on "Add payment method".
Select "Add credit or debit card".
Read and accept the terms and conditions.
Click on "Continue" to receive a confirmation SMS. Your phone number must be confirmed in your Internet bank account (in the "Contact information" section).
Enter the verification code received in the text message and your card will be added (when the card is successfully added, it will appear on the home page of the Google Pay app).
If you mainly want to pay with Google Pay, set it as the default payment method.
The card user can add additional cards to Google Pay if the user's phone number is verified and connected to an online bank account.