1. Back up all your important data such as photos, videos, contacts, messages, etc. to an online storage account, SD card, or computer.
  2. Access your Oppo smartphone's settings by tapping the "Settings" icon in the app drawer or on the home screen.
  3. Scroll down the list of settings and select "Backup & reset".
  4. Select "Factory Data Reset" or "Factory Reset".
  5. Confirm the action by tapping "Reset phone" or "Erase everything".
  6. Wait for the reset process to complete. This may take several minutes, depending on the amount of data stored on your smartphone.
  7. Once the reset is complete, follow the onscreen instructions to set up your Oppo smartphone as a new phone.

Note that factory reset will delete all data, apps and files stored on your Oppo smartphone. Therefore, it is important to backup all important data before doing the reset.