The steps given, in the link to a post on this site, does have the right info. Have you tried turning off the phone and then turning it back on to see if it shows? Also, was the phone perhaps rooted? If so, then that option could have been moved or removed. In such a case I could not help.
Now if restarting doesn't help, and the device wasn't rooted, you could try starting it up in "Safe Mode" and see if you can find the option then. It is completely possible that an app or other item on the device is hiding the option. So accessing the phone in "Safe Mode" would remove such a block.
To get into "Safe Mode" please do the following.
1. First turn off the phone.
2. Next press and hold "Power" until you see the manufacturers logo on the screen, then release the power button.
3. "Quickly" press "Volume Down" and hold it for few seconds until you see the message "Safe mode: ON" or something similar.
4. If you wanted disable it, simply repeat the steps above, and you should see "Safe Mode: OFF" rather than on.