I see you're running Mint? Look under the main menu for VirtualBox, possibly system tools but may be under a different heading. Start VirtualBox and the GUI will show no Virtual Systems. Select "New" and you'll be taken through the set up where you'll have to allocate disk space, say 20Gb?, etc. You'll also need your Windows CD/DVD to be loaded in your drive as the source. Follow the instructions...
Once the system's loaded, you'll get Windows as a choice within the main GUI. Select it and hit "RUN" and you're good to go.
Does this help or have I missed your point?