In NetNewsWire 1.x, I made sure the add-feed sheet was as simple as possible. My thinking at the time was that this was a moment of high anxiety, since subscribing to a URL was very much a brand-new thing. It looked like this — just one text field for the feed URL:
Note that it required the actual RSS URL — these days you can just use the home page URL and NetNewsWire will find the feed.
And, since this is no longer an unfamiliar thing to do, we can make the add-feed sheet a bit more useful. (Hopefully not too cluttered, though.)
So this is what it looks like in NetNewsWire 5: