Back up any important data
Charge the phone to at least 50%
Open Settings
Tap System or General management
Tap Reset or Transfer or Reset
Tap Factory data reset or Erase all content and settings
Review the items that will be erased
Tap Reset phone or Erase all
Enter your PIN, password, or pattern if prompted
Confirm the reset
Wait for the phone to restart and erase itself
Set up the phone again after it restarts