I'm going to go back further than what's been talked about. When I started, I had an idea (you're not going to get far as a writer unless you have an idea). My concern was whether I could transfer the emotions I felt in a particular scene into words on paper. So I wrote that scene. I looked at it, decided that enough of the emotions were there, and then went back and started the story. Whenever I got stuck, I would go back to that scene and tweak it, trying to bring out the emotions even more. That continued until the scene was ready to drop into the story.
So, before you go any further, imagine a scene and try to write it. If you're not sure you've succeeded, show it to someone and ask them not only if you think it's captured what you were trying, but if you haven't, what's missing. If you want a completely independent test, try doing one of the weekly prompts and posting it in Writing Prompts forum. It's good practise and an excellent way to help yourself develop. You can post the scene that's derived from the prompt in the forum thread if you like.