To Link The First Flame
This is probably the ending you’ll get on your first blind playthrough. To link the first flame in Dark Souls III, simply play through the game as per normal until you reach the final boss, the Soul of Cinder. After defeating the boss, look for the bonfire sitting near the edge of the boss arena.
Simply interact with the bonfire, and accept the prompt. This will trigger the cutscene for the first ending.