Find a large and recognizable space, e.g. Brooklyn Night Bizarre. The area will be set up with booths and stages, booths for the flea market and stages for music. Hold a show catering to young tastemakers. Tickets are free if you bring something to sell in the space using the Wallapop app. It will inspire first time users of the app, and anyone already on the app will see the large cluster of sellers and migrate towards the event. It would be fun way to appeal to a large group of tastemakers