Mangos usually need ripening after purchasing. When you bring mangos home from the supermarket, ripen them at room temperature, perhaps on the kitchen counter. To speed up the process, place them in a closed paper bag. To check for ripeness, smell the mango near the stem end. It will have a fragrant, fruity aroma when it is ready to serve. Mango connoisseurs also look for skin that has just begun to shrivel, which is a sign that the fruit is approaching maximum sweetness.