This is a massive question, and I have included some useful links below to help you get started as you begin researching this issue. The first thing that you need to know is that this is still a very important issue for Australia today as it seeks to come to terms with and confront its past attitude and actions towards Aboriginals and the various ways that it mistreated them since colonisers first landed in Australia.
You might like to also refer to texts such as The Secret River that explores this from a narrative viewpoint, or the film Rabbit Proof Fence, that looks at the way in which Aboriginal children were taken from their parents and kept in situations where they were abused and encouraged to forget their native languages.
Basically, the history of Aboriginal people is one of exploitation and oppression as the stronger and more advanced and organised white settlers arrived at Australia and found that they could easily dominate and subjugate the indigenous settlers. There was so much about the Aboriginal way of life that meant they were unprepared to deal with or confront a mobilised army of colonisers, and this lost them vast tracts of territory, leaving them with only the most brutal and unhospitable tracts of land to live on.