There are many domestic & international flights to Da Nang by VietnamAirlines, VietjetAir or Jetstar... It's a good idea to check airfares often because prices fluctuate all the time.
From Da Nang International Airport or city center: you can take a taxi to My Khe beach (5km), the fare is around 100.000-150.000VND or rent a scooter (rental fee ~150.000VND/day).
From Hoi An: taxi fare would cost from 220.000VND to 250.000VND/one way (25km). Please ask the taxi driver about the fee or ask your hotel staff to book the taxi for you, don't go by meter as the price will be much higher.