XML to CSV File

Hello, I have been asked to convert all of the stuff from here: http://www.rkwltd.com/xml2.php

into a CSV file to be uploaded to an ecommerce website. Please could someone explain to me whether this is possible with some sort of conversion software, I have tried a few options after searching Google, but they either don't work or I am not doing it properly. I am really stuck and I have spent half a day trying to work it out. I do not know anything really about XML, I have a mac so I'm limited to applications. Can anyone recommend an option. I have tried to download the info from the link, import into microsoft but it is not working :(

Thank you