Step 1: Go to the UPI app ( Google Pay , BHIM, PhonePe etc.)
Step 2: Tap on ' Bank account ' option.This section shows all the bank accounts linked with this particular app
Step 3: Select the bank account for which you want to set a UPI PIN. You will see a ‘SET PIN' option in case you have never set a UPI PIN for the bank account
Step 4: Enter the ‘Last six digits’ and ‘Expiry date’ of your Debit/ATM card