On a basic level all stories are a combination of 4 components; characters, a plot, a setting, and one or more ideas, which in this case refer to the underlying questions being explored. Ideas can be as simple as “how will the protagonist accomplish their goal”, or as complex as the purpose or meaning of life.
Use What You Have
Most stories start small; a character, a conflict, an interesting place. Whichever piece you have, start with that and build out.
Stories begin with a protagonist, a setting, and a status quo. Then something disrupts the status quo. This is the beginning of the plot. Plot constitutes everything that happens in the story; every event, action, or choice. The foundation of any plot is conflict. Conflict is any time a character has an objective with an uncertain outcome. Every conflict has two steps, the promise and the payoff. The promise is when you build the conflict up. The payoff is when you resolve the conflict.