Moving from writing purely dialogue with some stage directions thrown in has been a challenge. A friend once described to the act of writing a novel as filling a swimming pool with a syringe. Oh yes.
I write a section, and walk away. A few days later, I'll suddenly realize that I need to go back to that section and write in a character, or even just a beat or moment. It doesn't change the course of the narrative, but adds an additional layer to the story. It's more like "local color." And this happens over and over again. Write, walk away, add layer. Rinse repeat.
I have to constantly remind myself to stop and be fully present in my character's moment. What does the temperature feel like? What color are the walls in the room? Is there a carpet on the floor, or is hard wood, or tile? That small detail can change the sound that my character makes when she thuds, or scrapes, or shuffles across the room.
These moments are the syringe. The white space on my computer screen is the pool I am trying to fill.