Scenes make up the entire structure of your novel, so it’s important to know how to do this well. Very often, a new scene is identified by the start of a new chapter, but it can also be a few paragraphs/pages long. Identifying a scene is the first step.
Here is the technical definition: A scene is a unit of story that takes place at a specific location and time. If those change, you have a new scene. Your story will be illogical is it has no semblance of scene or scene changes, so this is very important.