Mounting Oracle VBox share on linux is much easier than you might think.
1. Install VBox tools on the linux guest operating system (VM->Devices->Install Guest Additions)
After the tools have been successfully installed configure a shared folder in Devices->Shared folders.
Write down the name of the share (Name of the shared folder).
The mount should be done automatically to the folder:
(Remember that only a root user will have privileged to that read/write to that folder)
Alternatively you can mount the folder yourself with the command:
mount -t vboxsf YourFolderName /home/user/vboxsharefolder
where YourFolderName is the name of the VirtualBox share,
and /home/user/vboxsharefolder is a previously created folder to which you have appropriate privileges.