Its quite normal to get pimples ( or acne) usually in puberty. Regular cleansing, avoiding too much greasy food, avoiding sugary drinks, moderate exercise that helps to clear out the pores, steam facials, drinking at least 1.5 litres of water a day, plenty of sleep - all help.
Don't squeeze or pinch them as they drive the bacteria deeper and leave marks. Simple cleansers/anti-acne preparations called benzoyl peroxide ( brand names vary) can be got straight from pharmacy. If its a severe acne problem than a consultation with Dr will help identify best treatment: topical gels, oral antibiotics or in really advanced cases with severe scarring- Retinol can be used. If it is related to hormones and periods contraceptive pills help a lot.