Take a look through the PowerPoint. It contains lots of interesting facts and important points.
Decide which is the most important or interesting thing on the presentation to you, and design a poster that explains that thing to a younger class.
You should include pictures, information, explanations and facts and figures. You could also find out more about your chosen topic using books and the internet. Try to make your poster as eye-catching as possible - People will remember your ideas better if its presented beautifully!