How to Install Extension Pack in Oracle Virtual box

In this post I'm going to describe that How you can install Extension in Oracle Virtual box.
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First Short Introduction of Oracle Virtual box

"Virtual box" redirects here. For virtual computers in general, see virtual machine.

Virtual Box may be installed on an existing host operating system; it can create and manage guest virtual machines, each with a guest operating system and its own virtual environment. Supported host operating systems include Linux, OS X, Windows XP and later, Solaris, and Open Solaris; there are also ports to FreeBSD and Genode. guest operating systems include versions and derivations of Windows, Linux, BSD, OS/2, Solaris, Haiku and others. Since release 3.2.0, Virtual Box also allows limited virtualization of OS X guests on Apple hardware, though OS x86 can also be installed using Virtual Box.

Guest Additions should be installed on the guest operating system in order to achieve the best possible experience. It consist of device drivers and system applications that optimize the guest operating system for better performance and usability. Since version 4.3 (released in October 2013), Windows guests on supported hardware can take advantage of the WDDM driver included in the Guest Additions package; this allows Windows Aero to be enabled along with Direct 3D support.