Back up any important files, because Developer Mode can erase local data
Turn off your Chromebook
Press and hold Esc + Refresh, then press Power
When the recovery screen appears, press Ctrl + D
Press Enter to confirm turning off OS verification
Wait for the Chromebook to restart and switch into Developer Mode
Follow the on-screen setup prompts
At startup, press Ctrl + D to boot in Developer Mode
If prompted, wait for the developer mode warning screen to time out or press Ctrl + D again