You can use Synaptic. But sometimes you get trouble using Synaptic versus aptitude/apt-get. If you deinstall some packages with Synaptic, aptitude wants to reinstall them. I only use aptitude, with the CLI or with the commandline.
Also, the kn-material would not come in via Synaptic, so
I used apt-get install; was that ok?
To install my package, why don't you use "dpkg -i"?

Read in the VirtualBox Manual how to create shared folders.

The other way to get an ISO out VirtualBox is using an USB-Stick. If someone has VirtualBox within a Linux Host, he can use a ssh-connection between Host an Guest.