Pull over in a safe, flat spot, hazards on, handbrake up, and pop a wheel chock or big rock opposite the flat—no heroics in traffic, thanks.
Grab the toolkit and spare, find the marked jacking point in your owner’s manual, and crack each wheel nut a turn before lifting (yes, lefty-loosey still applies in Australia).
Jack the car up, spin off the nuts, and lift the wheel straight off like you’re removing a stubborn pizza lid.
Fit the spare, hand-tighten the nuts in a star pattern, lower the car, then tighten firmly in the same pattern.
Check tyre pressure; if it’s a space-saver, keep it under 80 km/h and get the puncture repaired ASAP.
Stow the gear, collect your dignity, and wash your hands—preferably not on the seats your partner just cleaned.