Getting a volunteer position/work experience as a first-year law student can be difficult given how competitive the market is and because you will have limited legal experience, but I commend you for starting your search this early.
Volunteering at a community legal centre, even if it is just helping with administrative tasks, is a good place to start. Alternatively you could look at special interest groups such as the Asylum Seeker Resource Centre, Environmental Justice Australia, Justice Connect, Youthlaw, Consumer Action Law Centre, Human Rights Law Centre, Victoria Legal Aid and others.
You can also try cold-calling various law firms to see if they are happy to have you work for free in their mail room/general admin.
Another option is to check if your law faculty or law society runs a barrister shadowing program and apply for that.
Finally, most universities operate a careers page where you can search for sector specific volunteering opportunites or entry level jobs. You can also check out
https://beyondlaw.com.au/ to see if they have anything posted in Victoria.
Unfortunately the nature of the legal market at the moment means that even volunteering opportunities are often highly competitive. That said, if you can get your foot in the door, it makes it progressively easier to get the next job and to build your network of contacts.
As a general tip, you are likely to meet a number of professionals/mentors/supervisors during any volunteering/work experience stint. I highly recommend you keep in regular contact with them even after you leave your position so that they remember you name in case any other opportunities pop up. If someone gives you their card or offers to grab a coffee with you, make sure to follow them up on it. It is not unheard of for a lawyer to pass on someone's name/CV to HR because they have shown an interest in a career in law and have demonstrated initiative by maintaining professional contacts.
Best of luck with your job search!