As far as actual procedure goes you would probably apply through UAC or the relevent service for your state. Some universities allow non-year 12 applicants to apply directly to the university, and the best way to find out if this is applicable to the institution you would like to attend would be check out their website, generally under "future students".
Remember, if you are at TAFE now if you have not finished your qualification you are most likely no further qualified than you were before you did your course. If you are applying on the basis of a TAFE qualification before applying check out if your course is relevent, generally it needs to be of a reasonable level to accepted as entrance criteria. If you don't know there should be a TAFE careers advisors that can help.