Participating venues can be found here: https://worldrumday.diplomaticorum.com/store-locator
Appears to be 21 venues in NSW, 8 venues in Victoria, 8 in Queensland and 4 in Western Australia
T&Cs (NSW, ACT, VIC, TAS AND SA)
T&Cs (QLD, WA)
Edit: Appears you can just redeem by going into the participating venues URL. Make sure that you are at the venue and are ready to redeem it.