On the beginning, the best way is to connect to the host with "ssh -X -C" and to use the GUI VirtualBox to launch. Like this you benefit from the GUI to load a previously downloaded dvd, for example.
You can also start with an image found here also see http://virtualboxes.org
I use the openSUSE dvd and install myself. The only problem I have got is to get rid of the warning VirtualBox messages, but you can tick "do not ask again", before the machine loads in the background too fast...
After install you have to make sure sshd starts and the firewall is stopped or open. In YaST, be warned that after choosing to open Secure Shell, you have to clic on "add" to make it active, and make sshd launch in YaST, run levels.
Now we have to cope with systemd and systemd do not any more look at the old inittab. I install xfce to have limited graphical GUI when needed, but do not want to have it launched permanently so, from openSUSE forums:
Currently you have to change runlevels using ln -sf /usr/lib/systemd/system/multi-user.target \ /etc/systemd/system/default.target or ln -sf /usr/lib/systemd/system/graphical.target \ /etc/systemd/system/default.target Next systemd will have both set-default, get-default and the respective dbus methods for applications that want to change the default runlevel.