chromebox

I hope somebody can help me I'm at my wits end. I know just enough to get myself in trouble.

I have a chromebox that I installed openELEC on as a stand alone OS about 2 years ago I really want to upgrade to LibreELEC.
Here is what I have done.
First I tried to reset the box like I did when I installed OpenELEC but I soon discovered this won't work as there is no Chrome OS anymore.
So then I followed the directions here to paste the LibreElec update to the update file and reboot. I did this and rebooted it started and a quick flash of the LiberELEC logo appeared then the screen goes black? What did I do wrong? Did I put the wrong update in the file? I used the "Gereric AMD/Intel/nVidia GPU HTPC.

Is there any way to wipe the box clean and start from scratch with a complete new install?

Help please

Thanks joefizz

Quote from POTI

Hit ESC while its starting, you might be missing it. That should pull up boot menu. Boot to the installer and wipe the drive.

Thanks
Do I need a plug in key board for this to work?