tested on openbsd 8.0
prepare your computer by backing up all data.
disable secure boot and enable uefi boot in the bios.
see how to do this on a
thinkpad x1 or t14.
prepare an usb drive with openbsd installer.
for example,
on macos.
boot the installer.
choose (I)nstall and answer questions. for example:
Do you want the X Window System to be started by xenodm(1)? = yes Which disk is the root disk? = sd2 Use (W)hole disk MBR, whole disk (G)PT or (E)dit? = G Location of sets? = disk Is the disk partition already mounted? = no Which disk contains the install media? = sd1 Continue without verification? = yes
unplug usb drive with the installer and boot openbsd from the target drive.
see also