You can get it from the Play Store.

https://play.google.com/store/apps/details?id=au.com.mi9.jumpin.app

You can also get it from here

https://www.apkmirror.com/apk/nine-network-australia-pty-ltd/9now/9now-4-10-0-release/9now-4-10-0-android-apk-download/download/?forcebaseapk

Keep in mind that you won't be able to watch anything unless you are either in Australia or have a VPN that connects thru Australia.

You also need to register to watch 9Now.