Image: Naughty Dog / PlayStationOfficial screenshot from Naughty Dog / PlayStation.
Don't Go is the gold trophy for finishing Left Behind, the Ellie-focused story bundled with The Last of Us Part I. It unlocks at the end of the sixth and last Left Behind chapter, Escape from Liberty Gardens.
Start Left Behind from the main menu and play it through. The chapters alternate between Ellie's night at the Liberty Gardens mall in Boston with Riley and her search for medical supplies in a Colorado mall.