Randy Ingerman has an excellent tutorial on writing, using a method he calls the “Snowflake method”.
I claim that that’s how you design a novel — you start small, then build stuff up until it looks like a story. Part of this is creative work, and I can’t teach you how to do that. Not here, anyway. But part of the work is just managing your creativity — getting it organized into a well-structured novel. That’s what I’d like to teach you here.
Step 1) Take an hour and write a one-sentence summary of your story. Something like this: “A rogue physicist travels back in time to kill the apostle Paul.” (This is the summary for my first novel, Transgression.) The sentence will serve you forever as a ten-second selling tool. This is the big picture, the analog of that big starting triangle in the snowflake picture.
Step 2) Take another hour and expand that sentence to a full paragraph describing the story setup, major disasters, and ending of the book. This is the analog of the second stage of the snowflake. I like to structure a story as “three disasters plus an ending”. Each of the disasters takes a quarter of the book to develop and the ending takes the final quarter. I don’t know if this is the ideal structure, it’s just my personal taste.
As someone who finds it hard to get words out on paper, I’ve personally found this method very helpful in organizing my thoughts. Give it a try!