The PIN you use in your card-reader is the same as your card's PIN - the same code you already use for that card at a cash machine or retailer.
For further information on card-readers see https://digital.ulsterbank.ie/personal/ways-to-bank/online-banking/do-more-with-anytime-banking/card-reader-how-to-use-your-card-reader.html (opens in a new window).