https://wiki.archlinux.org/index.php/VirtualBox

https://www.oracle.com/technetwork/server-storage/virtualbox/downloads/index.html

Guest Additions:

mkdir /media/cdrom0
mount /dev/sr0 /media/cdrom0
sh /media/cdrom0/VBoxLinuxAdditions.run
umount /dev/sr0

Linux install:
modprobe vboxdrv