Need Help with ASROCK Z390 Phantom Gaming X

[Johnfrag]

Hi I need help modifying my bios, I have a ASROCK Z390 Phantom Gaming X

I have an RTX 2080 and would like to activate the card's REZ.

I have currently installed the bios version 1.20N [Beta]

https://pg.asrock.com/mb/Intel/Z390%20Phantom%20Gaming%20X/index.asp#BIOS

Unfortunately I can't manage to modify the bios so that I can flash it via the bios. Can anyone help me with this?