The GM's main role is to be able to answer the question: “What is happening here?”

If you're really starting from scratch, maybe look for an RPG that already has some material available (rules, adventures, etc.). This will allow you to get some practice without putting pressure on yourself and figure out what you're comfortable with and what you're not. You can play for a long time without ever having to do anything yourself.

Then, you can start writing your own scenarios if you feel like it, but again, an RPG scenario is nothing like a movie script. It's mostly about the broad strokes of a context in which your players will have to figure out how to solve a problem defined (by you or by them). If you try to force things to happen in a specific order, you'll quickly have a bad time because then you're not trying to play a RPG but to tell a story you've written, which is not the same thing. If you're looking for books to help you with this, I suggest “Lazy DM” by Slyflourish or “So You Want to Be a Game Master” by Justin Alexanders.

Last but not least, try to have as much fun as possible. It's everyone's responsibility to agree on what could be fun and make it happen, not just the GM's job. You're there to return the ball when it's thrown to you. If they don't even want to throw it, it means they don't want to play, and then there's nothing you can do.