After clicking the green flag, hit "Ignition". After the yellow lights stop, use the rods up and down button to control the temperature of the reactor. After ignition, you will get a power order. It is usually between 20-50 thousand. You must bring the Power Production to a range from 100 to -100 of the power order to complete it and get another one. Dont let the temperature reach 4000, or else the reactor will enter a meltdown state and you will have to fight the rising temperature to cool the reactor down.
Thanks to Joel Nielsen for the startup music and Vern Carson for the meltdown music. Thanks to FreeConvert.com for compressing audios. This is not meant or in any way to reference real-world nuclear meltdowns, this is just a cool simulation.