How do you use a spot treatment for acne?

Depends on the type of spot treatment you have, but all the external spot treatments are applied directly to the affected area on the skin. So if you have a blemish on your chin just apply the treatment directly on your chin. However if you are using a oil treatment e.g tea tree oil if it is neat ( not diluted) you may have to dilute it before applying to the skin, to avoid irritation.