First, choose a simple children's story. Then, identify the main elements. For example, the exposition is the beginning part where the characters and setting are introduced. In 'The Three Little Pigs', the exposition is about the three pigs leaving home. The rising action includes the events that build up tension, like the wolf trying to blow down the pigs' houses. The climax is the most exciting part, here it's when the wolf tries to get into the brick house but fails. The falling action is the start of resolving the problem, like the wolf running away. And the resolution is the end, the pigs living safely. This way, kids can understand the plot diagram easily.
You can start by reading the children's story aloud. As you read, pause at important points. For a story like 'Little Red Riding Hood', when you reach the part where she meets the wolf in the forest, that's part of the rising action. Mark these points on a simple plot diagram drawn on a board or a piece of paper. Explain that the start of the story, which tells about Little Red Riding Hood's journey to her grandma's, is the exposition. The moment the wolf reveals himself in grandma's bed is the climax. The falling action is when the hunter comes, and the resolution is when Little Red Riding Hood and her grandma are safe. Use pictures or simple drawings related to the story to make it more engaging.