How can I stop face acne?

Benzoyl Peroxide. The honest answer is that acne is not cured, its treated. Sometimes you will require seeing your doctor for perscription strength medication. You can start however with over the counter benzoyl peroxide soap and topical creams. They work pretty well for mild to moderate acne.
A few options. For over the counter methods try using products that have benzoyl peroxide, salicylic acid, alcohol, and acetone. For prescription treatments you may be prescribed antibiotics, retinoids or vitamin a derivatives, azelaic acid, oral contraceptives, or spironolactone. Always ask a dermatologist about the possible affects and the risks vs benefits of each treatment. Make sure it's best for you.