The main shop screen is where you are when you just click The Stash. You can access this just after death or by tapping the arrow in the top right hand corner of the main menu and then tapping The Stash. Simply stay here for two minutes. The trophy should unlock after the two minutes. Please note that if your Vita backlight setting is below two minutes, you can either tap one of the Vita's buttons to stop the system from hibernating without affecting the trophy or you can increase the backlight time from the Vita's settings menu.