If you are a creator that is registered for GST in Australia, you'll receive an automated message via the brief reminding you to provide an invoice in order to receive GST.
You'll need to generate an invoice for the Creator Payment amount with GST added (these amounts are details on the brief to make it easy for you), include your ABN, and include the brief reference number which can be found in the brief URL.
GST will then be released as a separate payment to collect via your Payments Dashboard.