Resetting your iPhone is simple:

1. Tap the Settings app.
2. Tap General.
3. Scroll all the way to the bottom of the screen and tap Reset.
4. On the next screen you’ll see six options. Select the below mentioned option:
5. Tap Reset All Setting to reset all settings (network, keyboard dictionary, home screen layout, and location & privacy settings, etc) back to default.
6. After choosing one of the above, enter your security passcode when prompted and then tap the red Reset button. Your iPhone may need to be restarted depending on which above option you chose.