Use following Steps :
1. Open your device’s Settings. The Settings app can have varying icons depending upon on your specific device, and may be also found within the App Tray or by pushing the phone’s dedicated menu button.
2. Find your Factory Reset option. Depending on your device, the “Factory data reset” feature may be located in one of two sections within the Settings app:
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Select the “Privacy” settings, and scroll down to “Factory reset.
3.
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Tap “Reset device” to delete all data and restore your device’s factory settings. The accounts that you are signed into will be displayed on the screen. By default, all of your phone’s internal storage will be wiped.
4. Confirm the process by selecting “Erase everything". This will delete all data and restore back to your device’s factory settings. Your phone will be as if it just came out of the box.