To use it topically, just wet a cottonball with a freshly squeezed lemon juice and dab it on your pimples. It might sting especially if the pimple is scarred. You can dilute it with water if pure lemon juice is too strong or stingy. Leave it on for a few minutes or even overnight, then rinse.
You can also squeeze lemon juice in water and use this as a rinse after cleansing your face. A glass of fresh lemon juice daily is not only a cool refreshing drink but also a great detoxifier. It cleanses the liver of toxins, allowing to effectively process vitamins and minerals that our body needs.