Thanks for reaching out! Adding more GM support is definitely a goal of mine going forward, as when I wrote this game originally it was very much geared for my personal playstyle as a GM-- that is to say, heavily improvisational and imagery-focused. Most of my planning comes down to coming up with cool concepts and then figuring out ways to throw them in front of my players to see what they do. But hey, that's pretty broad, so let's get into some specific advice!
One, lean on Rituals! The Ritual of Beginning is written to give a broad trajectory for a game that's just getting started, as well as to quickly tangle up the PCs' lives. Playing that out, letting the players explore the Named City for a bit, and then hopping into the Ritual of Sleep will probably eat up a good amount of your first session and give yourself and your players a nice taste of what the game has to offer. Other rituals, like Storytelling or Bloodshed, help to frame significant moments in a way that's not unlike GM moves in a PbtA game.
Two, pick one or two layers you really like and focus in on them. Pick out a few locations that speak to you, write some NPCs who hang out there, give one of them a knotty problem, and set your players loose. There's a lot of disparate (ha) ideas in this book, you don't have to worry about juggling all of them at once. If you take the advice from point one, just play around in the City and Dreaming for a while, and only expand out once you're comfortable!
Three, check out small business in the zine titled Seven Plays. It's a little adventure module, just a couple NPCs and story beats, but enough to get a story going if the above isn't cutting it. There's also Apoptosis but it's considerably less new-GM friendly, as instead of a clear goal and some stops along the way it gives you pregen PCs with an insurmountable problem and asks you to play out a bleak tone piece.
Lastly, remember the game's mantra: If it's interesting, you can do it / If you forget about it, ignore it / The City is wide enough for all of us. Don't sweat the details too much! The GM is a player too, and that means you should have fun with it! Get a bit silly with your friends, bite off more than you can chew, and when you inevitably make mistakes take them in stride and grow from the experience.
Hope you have a lovely time!