I would say start expanding on your characters first. Write out their likes, dislikes, goals, insecurities, along with basic biographical information like their age, etc. This will help you to pinpoint where your character is in life right now and acknowledge how they need to change to become a better character/person, and you can build a story around their goals.

6

Thing that really helped me: try to aggressively pander to yourself and make a story that is specifically targeted for an audience of one (you) to adore Try making a big list of the kinds of things you always love seeing in fiction (character archetypes, tropes, settings, etc.) and see if you can synthesize a bunch of them together

4

I would say think of the conflict of the story. This is what going to drive the narrative forward and it allow to think of concept scenes that you can add in your story

3

Think of what could be a life changing period for them. Do you have backstories for them? You could also consider what types of scenarios would bring out their best and worst and most fascinating qualities. Also, what do you imagine them doing or say when you daydream about them, even if it’s just tiny moments?

3