"what's the procedure / method of changing the [iTunes] URL?"
Simply change the title of your podcast.
iTunes uses your title in your URL. Change your podcast title (name) and your iTunes URL will change.
To get your URL:
Podcasts app: Tap the share icon at the top right and select "Copy Link". iTunes Store: Control-click on podcast artwork and select “Copy Link.”
Example:
Title: Long Range Truck Driver's Friend
iTunes adds your ID to the end of your title, creating the URL.
This URL will cause the podcast to load into the Podcasts app, or iTunes if they are available: https://itunes.apple.com/podcast/long-range-truck-drivers-friend/idNNNNNNNNN?ls= 1
(Note the URL ends with ?ls=1 )
This URL will bring users to iTunes Preview, a web page with info about your podcast: https://itunes.apple.com/podcast/long-range-truck-drivers-friend/idNNNNNNNNN?mt= 2
(Note the URL ends with ?mt=2 )