There's a simpler answer to the question "how do I use xterm," though. It is that you use it the way people used to use DOS. It gives you a command line and you type in instructions for the computer to follow. (And the command line is still used, of course, in Windows.)

Often, people give the exact instructions so you don't have to understand what you are doing very much. Some of the instructions are pretty clear -- apt-get update, for example, has something to do with updating.

But using a live cd like the one for Sidux is a great idea, and there are many great Linux tutorials out there.