To practise law in Australia you must first be admitted as an Australian Lawyer. In Victoria the process for admission is conducted by the Victorian Legal Board of Admissions. If you have qualified and/or been admitted in a country other than Australia (in some countries admission is referred to as "being called to the Bar"), the relevant information can be found there.
If, once you have been admitted as an Australian Lawyer or you have a reasonable expectation that you will be admitted, you want to join the Victorian Bar and practise as a barrister, please refer to Becoming a Barrister.