Exposition is a part of the story, but can not be applied to the story in its entirety. It's not like a theme or premise. So, saying "the exposition of the story" is incorrect.
When you look for exposition scenes, you are looking for scenes that have backstory, or background information -- the narrator is describing something that happened in the past in these scenes. Look for paragraphs that talk about the past.
For rising action, all you need to do is look for scenes (paragraphs in the book) that show the main characters, Harry, Ron, etc., doing something active that's kind of uncomfortable for them or thrilling--like a minor fighting scene or an escape scene.
The climax is a major action scene near the end of the book where the Protagonist (Harry -- the main character/good guy) triumphs over the Antagonist (the bad guy).