Apple iMac (21.5 and 27-inch, Late 2009) - Manual (Page 10)

10 Chapter 1 Ready, Set Up, Go
Setting Up Your iMac
Follow these steps to set up your iMac. Wait until Step 4 to turn on your iMac.
Step 1: Pass the power cord through the hole in the stand, plug it into the power
port on the back of your iMac, and then plug it into a power outlet.