No need to... Treatment of acne is something you do for someone who is embarrassed to appear in public (or on a date) with zits and pimples. I think it's safe to assume that a newborn is unlikely to feel embarrassment, and in any case acne goes away by 6 mo. I would suggest simply avoiding things that make it (and other skin conditions) worse, such as harsh soaps, rubbing, wet wipes, and overuse of steroids.
Depends. Neonatal acne usually goes away without treatment after a few months. It can be caused by a reaction to either internal or external factors causing irritation, inflammation or an allergic reaction. It can also be caused by hormones in the mother's breast milk. Switching to formula can help if hormones are the cause.
No. Baby acne is completely normal and harmless. It doesn't cause scarring like teenage acne can. It's best to do nothing about the acne. Often, parents will apply lotions, creams or gels, which only cause a new rash or irritation. It's best to wash the face with a gentle soap and avoid using anything else. Just be patient: the acne will go away.