Hi and welcome to the forum!
Growing sunflowers is pretty easy. Just make sure the soil drains well, water without overdoing it, and give them plenty of sun.
Since you're in the other hemisphere, the best time to plant would be between September and October, or November if you're in the south.
Are you thinking of growing sunflowers just for decoration, or for harvesting the seeds?
Keep in mind that some sunflower can research more than 2 meters tall.
They're also a great option if you want to attract birds to your backyard, they'll go crazy for the seeds!
In Spain, it's super common to eat sunflower seeds as a snack — salted and roasted, they're everywhere!