First, you should read about the story:
http://www.pitt.edu/~dash/type0124.html#lang
Once you have finished reading it, you should be able to tell the setting (Who are the characters? What are they trying to do?), the problem (What is the situation that the three little pigs face?), the climax (What causes you to continue to read the story? The fox/wolf? The way how they build their houses?), the resolution (How did the pigs defend their houses from the fox/wolf?), and the ending (What happened at the end?)
By answering the questions above and chaining your answers, you should also be able to summarize the story in about 40 words.