Once your feed has been accepted you are given the URL to the iTunes Store, which is presumably what the second link you have posted is.
You don't have to interact with the Store any further. Just add a new episode to the podcast and re-upload the feed. Subscribers will see the new episode immediately, but it usually takes the Store a day or two, occasionally longer, to catch up.
Incidentally I don't know where you saw the instruction to ping the Store, but that facility was removed over a year ago. (Not that it ever did much good anyway). The Store will update when it gets round to your feed.