If you installed Desktop Environment

If you installed Desktop Environment, it's possible to create Virtual Machines on GUI. This example shows to install Windows Server 2012 R2 on GUI.
[1]	Start [Applications] - [System Tools] - [Oracle VM VirtulBox].

[2]	Click "New" button which is on upper-left.

[3]	Select the OS type for Virtual Machine.

[4]	Specify amount of memory for Virtual Machine.

[5]	It's the settings for disks of Virtual Machine. This example shows to select "Create a virtual hard disk now".

[6]	Specify the type of Virtual hard disk. This example shows to select "VDI".

[7]	Specify the type of growing for Virtual hard disk. This example shows to select "Dynamically allocated".

[8]	Specify amount of Virtual hard disk.

[9]	Configuration wizard finished. For initial booting of VM, it's necessarry to install OS, so click "Settings" button to specify installation media.

[10]	Select "Storage" on the left menu and click DVD icon on the right pane.

[11]	Specify installation media.

[12]	Back to main menu and click "Start" button to start Virtual Machine.

[13]	Virtual Machine started.

[14]	Installation has finished and Virtual Machine is running.