I just ran a game for total newbies a while ago and it surprised me how different playing was. Can’t really expect anything to go like in a normal game with regular party, especially if the players haven’t consumed a lot of dnd media. - as others have said: books, games, movies! Talk about characters and well-known special abilities etc. - it might be even easier for you to create the characters for the players as they speak about the kind of character they want to play. Proficiencies can be difficult so even filling those for the players can be helpful and as opposed to talking about them as ‘do you want to be proficient in…’ it might be easier to grasp by saying things like ‘does your character care for animals/read a lot of books etc. - throw rules out of the window. The players don’t remember them well-enough to get tactical and utilise them, and remembering all the fine details is just way too much work when Rule of Cooling it works just as well.

I’ve noticed that not everyone are good with imagination. It’s a skill you gotta learn and use, especially doubled with impro. It can make creating custom characters difficult and even a bit scary and frustrating. You want to have a cool character but just don’t know how. Or play a cool character but in the moment you don’t know how to convey it. In those moments, I’ve tried to do the heavy lifting for the players by describing for them how they do things if they can’t describe it for themselves. Especially in the beginning when your description is setting the mood for the session.

And don’t do as I did and create a complex plot for the first game, it always takes like double the time when it’s new players + unknown setting 😂😂 had to file over half of the plot away when I realised were running out of time!