How Do You Change Your Pin Number In The Zillionz Atm I Would Like To Know How Does Barclays Pin Sentry Work?

I would like to know how does barclays pin sentry work? - how do you change your pin number in the zillionz atm

when you put your PIN number with a code that is in banks, as the generated code is already on the card and if so, how online banking login online to know what the code when changing the code every time