As the name suggests, you need to clear the second maze of the game, pretty easy, just eat all the Pac-Dots while avoiding getting caught by the ghosts, once you eat all the Pac-Dots, a small intermission cutscene will play and you'll get the achievement.
Also, make sure to eat the Cherry and the Strawberry after eating a few Pac-Dots in Round 1 and 2 respectively for a few achievements.