This question has popped up in the past on a few occasions, so if there is still someone out there who wants to know how to do it, here is the easy way:
http://www.howtogeek.com/66348/how-to-setup-rsync-backups-on-linux-the-easy-way/
http://www.howtogeek.com/66348/how-to-setup-rsync-backups-on-linux-the-easy-way/