The document discusses how to add a virtual hard disk drive to a virtual machine by choosing "Add Hardware" from the virtual machine menu, selecting "Hard Disk" and then either adding a new blank disk image or connecting an existing disk image file. A virtual machine can have up to 4 IDE devices and 15 SCSI devices, and the user must initialize any new blank disks before use and ensure existing disks have a compatible file system for the guest operating system.