Lets start processing our VM by creating the virtual disk.
vmctl create -s 4G vmdisk.qcow2
This will create a qcow2 format disk with 4GB size on your home dir. Its enough for OpenBSD to be installed on.
Next task is to install OpenBSD on to the disk. Make sure we have iso image on home dir then executer below command using root.
# vmctl start -m 1G -L -i 1 -r install66.iso -d vmdisk.qcow2 vm1
The command will start a VM named vm1 with 1GB memory , Local network with 1 interface, mounting install66.iso as optical media, and using vmdisk.qcow2 file as virtual disk. AFter its started, connect to vm1 using “vmctl console [vm id]” and proceed the usual OpenBSD installation.