Just the way you register any of your utility bills with your bank for online payment, such as Mobile, Electricity, MTNL, Gas, etc., you can register the URN with your bank for I-SIP by adding the same in your netbanking

Kindly find the below links guidelines for URN activation in your respective Bank net banking section -

Guide for SBI users: https://cleartax.in/s/add-isip-urn-number-in-sbi-netbanking/

Guide for Axis users: https://cleartax.in/s/add-isip-urn-number-in-axis-netbanking/

Guide for Kotak users: https://cleartax.in/s/add-isip-urn-number-in-kotak-netbanking/

Guide for HDFC users: https://cleartax.in/s/add-isip-urn-number-in-hdfc-netbanking/

Guide for ICICI users: https://cleartax.in/s/add-isip-urn-number-in-icici-netbanking/

Guide for All users: https://cleartax.in/s/how-to-add-i-sip-urn-number-in-other-banks-netbanking/