First, you need to call them up and tell them where you are located. If you are lucky, they may have a scheduled pickup near your area and you can request them to drop by so you can purchase a few boxes. The box is around $10 each. Fill up the box with stuff (you can take your time filling it up), then call them again for pickup.. and that's all there is to it.
Another option is, you can go to an LBC branch (not sure where in Melbourne since i'm from Sydney) then just buy the boxes from there.
Customer service of LBC is based in Pinas. So yes, they might not have the answers to all your questions, especially if it's to do with aussie locations, local contacts and so on.
By the way, noticed that you posted this almost a month ago so hopefully, nakuha mo na yung info na hinahanap mo about LBC boxes.