From the apps list (swipe to the left on the main screen) go to Settings -> Location -> Move the indicator next to Location services to the right to disable the GPS or to the left, to enable it.
Note: Most mobile devices require the GPS feature to be ON as part of the anti-theft feature (in this case Find My Phone feature), which allows you to locate your device if it's been lost in stolen. Bear this in mind before you decide to disable the location service.
If you don’t receive the email in the next 2 minutes please check your junk folder, and add [email protected] to your safe sender list.