If you are healthy, you only need to wear a mask if you are taking care of a person with suspected Covid-19 infection.
Wear a mask if you are coughing or sneezing.
Masks are effective only when used in combination with frequent hand-cleaning with alcohol-based hand rub or soap and water.
If you wear a mask, then you must know how to use it and dispose of it properly.
When and how to wear medical masks to protect against coronavirus
Before putting on a mask, clean hands with alcohol-based hand rub or soap and water.
Cover mouth and nose with mask and make sure there are no gaps between your face and the mask.
Avoid touching the mask while using it; if you do, clean your hands with alcohol-based hand rub or soap and water.
Replace the mask with a new one as soon as it is damp and do not re-use single-use masks.
To remove the mask: remove it from behind (do not touch the front of mask); discard immediately in a closed bin; clean hands with alcohol-based hand rub or soap and water. — WHO