Back up any important data
Make sure the phone has enough battery
Open Settings
Tap System or General management
Tap Reset options or Reset
Tap Factory data reset or Erase all data
Review the items that will be deleted
Tap Reset phone or Erase all data
Enter your PIN, password, or pattern if prompted
Confirm the reset
Wait for the phone to restart and erase all data
Set up the phone again after the reset completes