When you purchase your admission tickets online, you will have an option to select Koala Encounter's as an add on to your ticket. For a single booking of $20 - you are allowed up to 4 people in the encounter and receive 3 complimentary photos in 1 book per group.
Please visit here https://www.wildlifesydney.com.au/tickets/ to purchase your tickets and add on the Koala Encounter.