How do antibiotics help us with viruses?

They do not help unless they are given to treat or prevent a secondary bacterial infection, such as secondary bacterial pneumonia in the case of the flu, skin infections from scratching measles lesions, or other related secondary bacterial infections.

Antibiotics are only effective for treating or preventing bacterial infections. There is no equivalent drug for use in viral infections. Other than careful hand washing and other preventive precautions, prevention with vaccinations is the way to avoid viral infections for many of these conditions, but not all, such as the common cold which does not yet have a vaccine for prevention.*

*The viruses of the common cold mutate very quickly and easily and, before a vaccine can be developed and produced, the virus has already changed making the vaccine no longer useful before it is even put to use.