I only just found out how it is done myself and have started on the path.
You need to be over 18 for a start then you should contact your local NPWS (though they may not be very helpful as by law they cannot recommend anyone) or contact your local native fauna control business and ask them for details, this is what I did and I begin my course this Weekend (very nervous
) MAKE SURE THEY ARE LEGIT AND ACCREDITED.
Then you need your First Aid certificate, two written references from experienced catchers/breeders to state you know what you're doing OR two years experience keeping venomous snakes yourself.
Finally, you take your new certificates and paperwork to your local NPWS for the necessary licensing in order to handle wild native fauna.
However, merely doing a course will not mean you are ready to start your own business up and catch reptiles yourself, try getting some work experience/on the job training from the Native fauna controllers you find or they should at least be able to give you contacts.
If you were in my area it would be simple to PM you the details of the bunch I am doing mine through.
Best of luck.