Big producers in Hollywood have an established line of financing available to work on new films. Smaller producers and independent producers need to come up with funding on their own.
The producer begins with a script. This could be a script they wrote themselves or a script they got from a screen writer.
Pre-production stage of film development has begun. The producer calls a director who would be in charge of everything on set, and would turn the producer's script into reality.
Then they talk about and invite everybody else on set.
Producers usually work with somebody they know. And there's a good reason for that, they need to be confident the director they call can do the job, and that they will work with the person well.
To become a good producer, it's a good idea to at least understand the jobs of all the people working in film. Even though all you're doing is giving directions, you need to know which directions to give.
You would also need "soft skills" experience. Been the boss is not just about ordering people around. You need to be able to work with different personality types, listen to suggestions, and sometimes convince an actor to not quit on a project.