You can only be sent a parcel to a post office using a parcel collection or parcel locker service. To sign up for this service here: https://auspost.com.au/receiving/collection-points/choose-a-post-office-for-deliveries
A parcel collect or locker address will look something like this and can be used with our website:
Address line 1: Parcel Collect 00000 00000
Address line 2: 123 Post office/locker Address Street
Suburb
State
Postcode
Do NOT send a parcel directly to a post office as it will be returned to sender and incur redelivery fees of $20.