How to add episodes to my podcast channel

If you are using a feed, which is the most-used method, you just add the new episode there - how you do so depends on what method you are using to make your podcast, but presumably rather than hand-writing then feed you are using one of the services which do this, you will need to add the episode usingn their method. If it isn't clear, approach their Help of Support. Once done and the feed re-published you don't need to do anything at Apple's end, it will happen automatically, but it may take up to a couple of days for a new episode to appear there.

If you are making your podcast directly in Podcasts Connect you will need to enter the details there, though I can't help you on specifics as I no longer have acces to it, no longer having a podcast. It should be self-evident.

If you are using a service to make your podcast it's there that you add your episode: you don't have to log into Apple, just adding the episode an uploading the feed will do it.

If you are not using a feed, log in at https://podcastsconnect.apple.com and add your episode there.