VirtualBox Linux – Add VBoxGuestAdditions
If you don’t have the vboxguestadditions.iso for your virtual machine, you can download it from here :
Rename the VBoxGuestAdditions_2.0.4.iso to VBoxGuestAdditions.iso and copy it to the /usr/share/virtualbox folder. Change the permissions so normal users can access the iso. Now you can install the Guest Additions in Virtual Box from the Devices/Install Guest Additions menu.