Coreboot question

This is not totally related to Purism per se but will be. Bear with me.

I have a Lenovo x-230 that has qubes oni it and has coreboot seabios on it (I hope that’s the correct terminology. I want to reinstall qubes but don’t know how to go about it.

When I bring up the boot sequence via ‘esc’ I am faced with an unfamilar menu which does not show a usb option where I would from boot from and install another os.

I am intending to dive right into a Purism v14 soon which has the same coreboot I gather so I want to be able to do the same to that as some point.

Is there a guide to how to doing this somewhere that someone can point me to? Or any advice?