Wait for the weather to break. Night temperatures should be consistently above 50°F/10.00 °C. Prepare a nice rich planting bed in a sunny place that is free of rocks & weeds, amended with rotted compost. The soil should be loose, dark & fluffy. Scatter the seeds about and barely cover with soil. Keep the seeds moist until germination in about a week. Alternatively, you can start the seedlings in cow pots indoors in February. Plant them out in April.

Well the fact you have poor soil is good as they are quite happy in poor soil. but they do need moderately good light.

I'd start them in 3" pots either in autumn or in spring. Use a soil based compost suitable for seeds. In the UK I use John Innes No 1 mix and either start them off in late August early Sept or wait until Feb/March. I usually put 2 seeds in a pot watered well and leave. Germination I find is any where from a week to 14 days. when they germinate they will produce 2 quite fat leaves then the next leaves are the 'true' leaves and have several leaflets per leaf.

at this stage gently repot them into slightly bigger pots.
now this is where I am ignorant. Do you get frosts? if you do then don't plant out either in the soil or in a nice pot until they are not expected.

there are some lovely dwarf varieties too which would be better in pots.

welcome to GoY too :o)

They should be fine in Melbourne . . . there are masses growing wild just across the sea in New Zealand!

Since Melbourne has a subtropical climate--cooler than mine, but maybe not cool enough--I would start them in fall, possibly as late as late April, since the seeds need cool conditions to sprout. The more commonly available Lupinus polyphyllus hybrids, such as Russell, may perish in the hottest, most humid part of summer. Of those, I would look for the shorter strains, since they are more likely to bloom before they cook!
With other lupines, choose your species carefully, since I would bet that some, such as Lupinus succulentus, could escape and become quite the pest! The Victoria equivalent of our Department of Agriculture will probably have lists of acceptable species.

They are early bloomers and you have to keep the weeds away. My lupins only lasted 3 years, getting successively smaller each year. I would continue to plant fresh seed each year.