What are you an expert in? In which topic do you ALWAYS have the last word and most up to date information? Be it football, fashion, politics or astrophysics, choose your topic and either talk or write about it.
Oh, and I forgot to mention one small detail: what you are saying is aimed at your 90 year old neighbour who knows NOTHING about it at all so ... Be as clear and engaging as you can!
We are looking forward to learning about your topic in the journal!