You can apply for a change of name by going to this link. Your you can tell people you are Mrs Smith instead of Mrs Jones so you don’t need to legally change your name however all legal documents must retain your previous name. All signatures are attached to your previous name too so no point changing your signature unless you are going to change your name. In Australia you do not need to fill out any forms to change your name if you are taking the name of your spouse. However it may make it easier to change your name anyway. You may both wish to change your name to something new. Some states have online processing. See the link below. http://australia.gov.au/topics/law-and-justice/births-deaths-and-marriages-registries
Certified copy of your marriage certificate
You can get a certified copy of your marriage certificate here. You most likely wont need one but if for some reason you do you need to apply in the state where you were married.