Hi!
Follow these steps:
1. Turn the power off.
2. Press the volume down, home key, and power key all at the same time.
3. Release all of the keys when a message pops up asking if you want to delete everything.
4. Press the power key to confirm the reset.
5. Other messages will pop up asking if you are sure you want to do this just keep pressing the power key to confirm the reset.
Hope this helps!