As of 16 March, 2020, face masks are not recommended for the general public or workers that are not directly exposed.
If you have respiratory symptoms like coughing or sneezing, experts recommend wearing a mask to protect others. This may help contain droplets containing any type of virus, including the flu, and protect anyone within three to six feet of the infected person.
The CDC offers more information about masks. The WHO offers videos and illustrations on when and how to use a mask.