Back up any important files from Google Drive or an external drive
Sign out of the Chromebook
Press and hold Esc + Refresh, then press Power
When the recovery screen appears, release the keys
Insert a USB flash drive or SD card with the Chromebook Recovery Utility image
Follow the on-screen instructions to reinstall ChromeOS
Wait for the recovery process to finish
Remove the recovery media when prompted
Restart the Chromebook
Set up the Chromebook again
If needed, perform a factory reset by going to Settings
Open Advanced
Select Reset settings
Choose Powerwash
Confirm the reset and follow the prompts