To turn your iMac on, you have to locate the power button. When you’re looking at the front of your iMac, the power button is located on the left-hand backside of your computer. The power button is located is around 2-inches from the far left-hand side and 2-inches up from the bottom edge. If you’re looking at your iMac from the back, you’ll see the power button in the lower right-hand corner.
Now, all that’s left to do is press the power button and wait for the boot-up chime. If your iMac is not turning on, please check if your power cable is connected to the power supply.