New
#11
On the Devices menu where your DVD drive is shown as drive 'G', click on it to select it. It needs to show a checkmark next to it before you can access it in VB.
The VBoxGuestAdditions.iso and More CD/DVD Images are so you can use the .iso image file of a DVD/CD in lieu of a physical disk. You can also use image files of floppy disks as well.
Quote