Undo the radiator cap.
Idle the car for a good 10min give it a rev every now and then if you feel like it
You should notice the coolant bubble away.
Coolant doesnt boil very easily so these bubbles are air bubbles in your system.
Sit back and wait for the coolant to get nice and hot.
You could even have the aircon on full hot this will help as well
After it stop bubbling put the cap back on an enjoy
Good luck