Flights
To
Kauai
Michelle Maria, no changes CC BY 3.0, via Wikimedia Commons
The aiport in Kauai, Lihue Airport, is located on the south east part of the island.
You can go to Google Flights to book a flight right now.
If you want to visit multiple islands or even just make a day trip, flights between islands are fairly cheap. Roundtrip, it will likely be less then 100$.
map made by creator of website