Originally Posted by lord_didger
As far as I understand I am supposed to mount VBoxGuestAdditions.iso and install this within my virtual machine but I can't find it within my debian...
Start the machine then select "Install guest additions" from the menus. This will mount the cd image in the virtual machine's cd drive (which is part of th e install package, no need for downloading anything).
After that navigate to your cd drive (/media/cdrom or the like or in the graphical interface the cd will show up in the file manager). Open a terminal and launch the relevant executable in it with root rights (it has to have linux and your system type, x86/i386 or 64 in its name).
BTW I think Debian has the vbox drivers built in but im not sure.