Steps 31-47 of this guide to install Ubuntu on a virtual machine (using VirtualBox) describe how to attach the Ubuntu instal ISO image file to the IDE Controller of the virtual machine.
This has not been mentioned or explained in any of the YouTube tutorials I watched on installing Ubuntu to a VirtualBox VM. I have no idea what it is doing or what it means. Is this a necessary step? What does attaching the Ubuntu ISO file to an IDE Controller mean?
The CD icon on my VirtualBox Manager under the IDE Controller section in the Storage setting shows a CD that reads "Empty" at the moment, which is the same as how it is in the guide before they change it to be lined with the Ubuntu ISO file.