You can whiten your teeth with coconut oil by doing what is called oil pulling.
To oil pull the coconut oil you rinse your mouth with the coconut oil by pushing and pulling the coconut oil through your teeth.
You don't gargle the coconut oil like you would mouthwash but you do push and pull it through your teeth.
You could also brush your teeth with the coconut oil to help whiten your teeth as it worked for me.