Be sure to evaluate your system’s Basic Input/Output System (BIOS) before installing OpenBSD. Because every BIOS differs, I can’t offer exact instructions on configuring yours. Your best bet is to consult your motherboard’s manual or the Internet.
Also, if your BIOS needs updating, take care of that before installing OpenBSD. Finally, check the boot device order, and be sure that it makes sense for how you plan to install your system.
With your hardware set up, get the boot media.