I'm running Ubuntu, so I'm guessing it's similar. Here's the guide and the link:
Installing XBMC Ubuntu 9.10 Karmic or higher
If you are using Ubuntu 9.10 or higher, you have the option of a more streamlined install. Load the terminal window and issue the following:
sudo apt-get install python-software-properties pkg-config
sudo add-apt-repository ppa:team-xbmc
sudo apt-get update
sudo apt-get install xbmc xbmc-standalone
sudo apt-get update
HOW-TO install XBMC for Linux on Ubuntu, a Step-by-Step Guide - XBMC
Good Luck!