add vboxmanage to path code example

Example: how to enter Vbox manage commands

How to use virtualbox command line?
VirtualBox command line
Make sure the virtual machine that you want to modify is shut down.
Tap on the Windows-key, type cmd.exe, and hit the Enter-key to start a command prompt window.
Type cd C:\Program Files\Oracle\VirtualBox to switch to the VirtualBox root directory.