Inhale through the nose and exhale through the mouth!
Your diaphragm pulls air into ur lungs. for example...take a plastic cup and cover the opening with a balloon. Put a hole in the bottom of the cup. Now pull the balloon down (away from the cup). The result is that the balloon pulls air into the cup. In our example the balloon is your diaphragm.
Your body is magnificently designed, that breathing (inhaling/exhaling) is a biochemical reaction due to the amount of CO2( carbon dioxide) accumulation not a deletion of O2 (oxygen) which triggers the mechanism to cause one to breath.