VirtualBox + .iso Ubuntu distribution file

[jaoc12]

Dear Ubuntu community
I'm a complete newbie. I'm trying to install this Ubuntu distribution https://lucenaresearch.com/community-news/downloads/ in VirtualBox as I run a Windows OS in my laptop.
I've followed the instructions in http://www.psychocats.net/ubuntu/virtualbox, but when I download and unzip the Ubuntu distribution from the first linkkn (the QstkUbuntu.iso), I end up with a folder with various files and subfolders.
So whenn in the tutorial (second link) it arrives to the step whereby you have to select the .iso file, I don't know what to do bcse I have no such .iso file, but the aforementioned unzipped folder.
Any advice/idea/suggestion?
Much appreciated.
Kind regards

[snowpine]

Don't unzip the .iso file.

If this is your first time with ubuntu, you might want to download it from this trusted link: http://www.ubuntu.com/download/desktop

[ibjsb4]

Note:

It is not necessary to burn a cd/dvd, You can install straight from the physical hard drive to the virtual drive.

[Warren Hill]

The iso file is a disk image. Virtual box already knows what to do with it. So you don't need to do anything with it first. Just select the file.

Also I'm not sure if you should trust the link to the iso file. It may not be what it seems. I have no particular reason to distrust it except its not an official Ubuntu site.