Good morning. Once the flash drive has been prepared, plug it in to the AIO. Turn the machine on and start
tapping the F2 key to enter the Settings menu. Once in, select Secure Boot Disable. Click Disable, then Apply.
Next select Advanced Boot Options and set Enable Legacy ROMs. Click Apply then Exit.
The machine will restart, so quickly start tapping the F12 key to open One Time Boot Menu.
Under Legacy Boot select, using the arrow keys, USB Storage Device and press Enter.
The machine will boot from the flash drive.
Follow the prompts for Language, Time and Keyboard and click Next
On the Install Now page at the lower left click Repair your Computer (see attachment)
Click Troubleshoot, Advanced Options and select Startup Repair (see attachment)
Let the process run and once done you should be able to boot up normally.