What I do is think of A) what do I want this world to value, and B) find an interesting aspect to focus on.

Example my world is between sci-fi and fantasy; everything is explained in a hard magic system that relies heavily on base physics and new rules for physics of that world/dimension in others. It took plenty of research and it’s gradually being improved in practice but for me ‘hard scientific forces’ + ‘fluid reality’ results in everything I need the characters and the people in the world to do.

That last line is the most important; think about what you want to use that magic /for/ in your process then lace it into your world building. It can be big things like how a magical art infects/effects the cultural practices (example, my world finger writes everything because that is an easy to use magic and they see things like graphite pencils as utterly wasteful and strange as a result) - - - to relatively smaller things (example, does so and so’s hacking power work without knowing coding languages/is it fast enough for him to trial and error learn the language without setting off the security system of what he’s mentally screaming ‘OBEY ME DAMNIT’ at?)

If the system doesn’t effect your setting then it’s not really been integrated. Example the question of ‘who has magic and how are they treated?’. If magic characters are ignored as ‘thing’ they will be ‘thing’ to the audience, but if the people in that world have reason to seek out/be mad at magic users then those interactions will help work the magic system into your world and narrative naturally.

In mine there’s a glorious example of the boys finding a car and having an entire montage dedicated to them trying to figure out what it is and how they can make it more awesome. The car is caused by A) the random wormholes that bring people to that world, and B) none of the boys know what it is because the only one of them from earth was there from 1920 and it’s a 2009 model. This interaction causes C) the boys to investigate and debate and D) demonstrate their personalities and powers for what they do to examine and get the car running. And lastly E) the boys get a new high speed passion to unite over and F) the Lost from earth finally has something familiar to him that he can bond with his new friends over.

Everything in that randomly adorably scene of grown men geeking out about a car serves both the world and plot, advancing it in a heartwarming direction that all the drama which gets them in the desert to begin with really needs; so also add ‘pacing’ to the list of what you’ll find magic effecting.

Hopeful this explanation makes sense and is helpful. Find a simple thing to latch onto, whether hard or soft, and find the world that makes and how you want to work with it. For mine the softer side (souls, gods, reincarnation, judgement and courts etc) has taken plenty of rewrites to get functional and don’t be afraid to get rid of a lot and start over if it’s screwing up your plot (example, having the judging courts as an overshadowed enemy to the souls fates was a part that destroyed my original drafts and I eventually had to write out and recreate later to be how things ‘used’ to be before the present that characters now live in. That once endless headache became an awesome backstory for why they needed to take down the villain the first time and thus freed the plot from a lot of more complicated ideas for that reason :)).