Air is needed for composting bacteria to thoroughly break down plant material. Aeration can be accomplished by regular turnings of the compost pile, preferably weekly. A pitch fork or spading fork can be used to turn a pile.
Plastic perforated pipes can be laid throughout the pile to increase air movement.
If the temperature of a pile drops, the compost needs either moisture or aeration.

The following video provides you with the correct English pronunciation of the word "COMPOSTING--AERATION", to help you become a better English speaker.