To have a easier time getting the achievements in this game: Pause the game, go to Game Settings, select 5 lives and activate Round Select, you will get the achievements with ease this way
The achievement explains itself, once you eat a set number of Pac-Dots, a cherry will appear below the Ghost Gang's Regeneration Chamber, also known as Ghost House, Unliving Room, Ghost Room and Spectral Callback Zones, whatever you want to call it (basically the square where the ghosts go to after getting eaten by Pac-Man), eat it and the achievement is yours, tho be careful and quick, as the Cherry disappears for a while.