The two parts of Freytag's pyramid that are addressed in the first chapter include the exposition and the rising action.
Exposition addresses the introduction of characters, situation and setting. Here, we learn that the fair boy is named Ralph. Ralph is a strapping young 12 year-old excited to be away from parents and adult supervision. Another boy is Piggy, a fat, seemingly a bit younger, smart, asthma-infested excuse for a boy. The setting takes place present day (which would have been in the 40s-50s) on a deserted tropical island. The situation seems to be that a group of boys have landed on this island without any remaining adult after a plane crash.
The events of the rising action revealed in the first chapter include trying to assess the situation, discussing how to get rescued, enjoying freedom from parents, exploring what the island has to offer, and determining where the other boys are on the island.