My host machine, that is the machine running virtual box is a Mac, and I’m trying to share a folder with a Windows 8 environment I’ve created with my virtual box.
After you have created the shared folder (located at the bottom right hand corner with the folder icon), you will need to install guest additions. Going to Devices > Install Guest Additions appeared to do nothing for me. On some version of windows, you get a notification pop up on the right hand corner, much like this video, for me nothing happened. Or so it seemed… What actually happened was that virtualbox guest edition installer was now mounted to my D drive but due to the steller UI and UX, it’s completely non obvious to the user as to what just happened. Anyways, you should be able to see it via windows explorer. Install the right version of VBoxWindowsAdditions executable, for me it was VBoxWindowsAdditions-x86. Once you’ve done that, the shared folder should now appear in your network drive.