Android XML Parsing Info for begginer

[Conky]

Hello I have a huge problem understanding XML parsing in Android since yesterday.I've tried SAX , Jsoup and XMLPullParser with no luck several times.I'm tring to build an app for getting the Nasa's RSS feed from the web and displays it in my app.The link is there :http://www.nasa.gov/rss/image_of_the_day.rssIt is an exersice from the Head First Android Development book .Would please someone provide some info for begginers with explanation about how an XML parser works? I've read SAX is one of the best options since it required less memory .Thanks in Advance