I'm in the middle of making my first game, but I have a lot of experience with short story writing.
A few probing questions:
What does your character care about? What motivates them?
Is your fantasy world peaceful or hostile towards your main character?
Are there villains in the story? How do they view your main character?
Does the main character have any allies? How did those relationships form?
These are a few ideas. Maybe just start by writing out by answering these questions and the story might start to develop itself!
Good luck!