Answer

Please click on the M-Flash button with flash drive icon on the upper right section (See attachment), or press "Ctrl + M" hotkey in BIOS menu to enter M-Flash Mode.

Reference

Models

PRO Z890-P WIFI, MEG X870E GODLIKE, PRO Z890-S WIFI, MAG Z890 TOMAHAWK WIFI, Z890 GAMING PLUS WIFI, MEG Z890 UNIFY-X, PRO Z890-A WIFI, MPG Z890 EDGE TI WIFI, MEG Z890 ACE, MEG Z890 GODLIKE, MPG Z890 CARBON WIFI, MPG X870E CARBON WIFI, PRO X870-P WIFI, MPG Z890I EDGE TI WIFI, MAG X870 TOMAHAWK WIFI