Apple Maps has quietly rolled out indoor maps for three new international airports, bringing the total number of supported airports to 37. The new airports include Sydney International (SYD), Edinburgh (EDI) and Hamad International in Qatar (DOH). You can find the complete list here on the iOS Feature Availability site.
Indoor mapping of airports and shopping malls is something that Apple Maps has been focusing on over the course of the last several years. While it is fair to say that Google is certainly ahead with Google Maps in this type of indoor mapping, Apple continues to chip away at catching up.
If you are at an airport where internal mapping is done, you can open up Maps and as you zoom in, you will start seeing the internal layout of the terminal as well as stores and eateries in that terminal. You can also go up or down on levels of the terminal if it has multiple floors.
There is nothing you need to do on your end. The updates are added on the cloud side by Apple so when you go to these new airports or existing airports, you will automatically get the indoor maps presented to you.