Now that you understand the mechanism of the throw, your goal is to catch your opponent at the exact moment when they take a step and both their feet become close to each other.
If you miss that opportunity you will have to wait and keep dancing and using footwork until the opportunity presents itself again.
Perfect timing is a skill like any other skill you learn in judo, you have to drill it with your training partner for hours and hours until it becomes second nature.
You shouldn’t be thinking about it, you have to feel and execute it without thinking, just like a reflex. This will take time to build, this the difference between a high-level judoka and an average one.