When a koala joey is born, it is helpless and relies on its mother for everything. Slowly but surely, the joey will begin to learn how to do things for itself, including climbing.
At first, the joey will simply cling to its mother's back as she climbs. However, as the joey gets older and stronger, it will begin to climb on its own.
The joey will learn how to climb by watching its mother and other koalas. It will also learn by trial and error. Sometimes, the joey will fall out of a tree, but it will quickly learn from its mistakes.
By the time the joey is about a year old, it will be able to climb confidently on its own.