Hello! 💖
Here is a simple step by step of how I do this kind of lighting in Clip Studio Paint. Will be using this piece I recently drew of La Signora ~
Made a colored and non-colored version to show the shape of the "spotlight" I do much more clearly.
I'm still practicing this technique so this is definitely not the right and only way to do it. Feel free to experiment especially with different/ multiple light sources (this one has another one behind her) 😄.
Hope its helpful!