In the Oracle VirtualBox, to add a shared folder to a Linux guest, open Devices>Shared Folders... and click Add Shared Folder (a tiny "plus" icon on the right). Then fill folder path and folder name.
> sudo mkdir /home/shared # creating mount point
> sudo mount -t vboxsf VShared /home/shared # use previously filled folder name
After every reboots the mount command is needed to repeat.
To do it automatically, just add the following lines to fstab.
> sudo echo "VShared /home/shared vboxsf rw 0 0" >> /etc/fstab