If you head outside as soon as it's dark enough to see the brightest stars and look above where the sun has set, you should see three objects clearly. The upper two will be reddish - the planet Mars and the gas giant Antares (in the constellation of Scorpius).
Lower-down, Mercury should be visible as a somewhat whiter object, as can be seen in the image below (from EarthSky.org). Note that this chart references South Africa. That matters not one little bit as South Africa is at the same altitude as the southern Australian states and will have identical conditions (merely a few hours later!).
Although setting as much as 2 hours after the Sun, much of that time is spent in the after-sunset glow, so it will really only be visible for perhaps 45 minutes in the mid evening.
Mercury reached its maximum apparent distance away from the Sun a couple of days ago, but will remain a fine sight for a few days to come.