This sounds like it will a fairly easy assignment since it is about a topic directly related to you. You can choose anything that has happened in your life that you remember a lot of detail about.
I would include in the first paragraph specific details about the event. Include the five W's: who, what, when, where, and why. Describe everyone that was involved, what happened, when and where it happened, and why it happened.
The second paragraph you can describe how the event made you feel. You can also include how it made others feel.
In the third paragraph you can write about any effects the event had on you or those who were involved in the event. You can also include how things would be different if the event never happened or happened differently (or you reacted differently).