i'm not sure on your degree rules, but most likely you will have to do the compulsory commerce and law units. you should get some papers tomorrow showing you examples of degree structures.
enrolment varies, if there is a que or not. most likely there will be cuz eeveryone will be as lost as you. you have to get a student handbook from the student centre first off before you enrol so you know what to pick. i suggest getting there an hour befor eenrolment cuz there will be a long line most likely. you have to fill out some forms like your details and your tax stuff for hecs, pick yoru subjects, and then pay your student fees and collect your student card.
you will need to pay your student fees tomorrow as well, thats $570. you don't need to buy any of your textbooks just yet, you will get told on what to buy in your lectures.
don't forget to bring yoru tax file number, your student admin fees, a passport sized photo (2 needed if you need a private bus company concession) and some form of ID just incase. oh and don't forget your letter of offer!!
they don't exactly make it clear to on what to do step by step, but just ask someone.