How to use. If not what it is for?

It looses secretions of airway.

It’s a mucolytic used to loosen up respiratory secretions

Indirectly it does help heal you. Mucus is secreted by the goblet cells found in respiratory mucosa. This mucosa lines your nose, paranasal sinuses, eustachian tubes, middle ear, mastoid air cells syatem, lateral aspect of your throat, larynx, trachea, bronchi and the alveoli in the lungs. This is collectively the Respiratory System. This mucus forms a thin sticky layer that is akin to the conveyor belt system that you seen in airports conducting your luggage from the baggage hold. In your respiratory system the mucus traps dust and other pathogens and conducts it from the nose, lungs and ears towards your esophagus. During this processes, your immune cells inactivate/destroy the pathogens and the debris is constantly and continually conducted towards your stomach whereon you finally excrete it out along with your faeces. However when you have a respiratory infection, the germs infecting your respiratory tract, transform the mucus into a thicker, more viscous liquid, to slow down this muco-conductive system. n-acetyl cysteine acts to thin out this modified mucus to restore its structure, thereby allowing your muco-conductive system to clear out the congestion. When this is happening in your middle ear, and mastoid system, it helps your other medicines like antibiotics to reach the disease causing germs better and thereby heal you.