I think they accept ongoing stories, and you just have to add the tag #featured to your story, that’s it. But honestly I think you have to be exceptionally lucky for them to actually go through the tag and read your story. I could be wrong, what do I know. With the old featured list, you submitted a form and they chose the best books from each genre. Now they pick a small handful of whatever they like, meaning some genres rarely have any featured books and you can’t search through them based on genre, which sucks.
It’s better to look at the profile pages like Fright or Romance,they have links to forms so you can submit your book. They accept anything in that genre as long as grammar is relatively good but that means there are some not very good books on their lists too, the quality doesn’t have to be high, just spelled ok. There are all sorts of profile pages like Project Woman Up, which is about empowering female characters, or Project Bad Boy. They are user run profiles, not official ones, and they accept books for their reading lists. Their profiles will tell you how to submit.