It is also called JustPlay (app is called OneGame)
You will need to download the app and create an account.
Typically it costs ~$17 for basketball, but with the code it's free.
Code is obviously generic. Said it ends at midnight, but it is passed midnight here in Melbourne anyway.
You can book any game that is visible, not just today/tomorrow.
Good luck and please show up if you book a spot.
Also, some stadiums charge an additional fee circa $2.50, but it will identify this when looking at the game before you book.