Check if XBMC is already available for this Ubuntu release: XBMC (roadmap)
If XBMC is released for Ubuntu 10.04, you can proceed with the normal installation, otherwise you have to install from SVN.
If XBMC is available for this Ubuntu release, the installation is as follows:
Now open a terminal window and execute the following commands:
$ sudo apt-get install xbmc
If XBMC is not released yet for this Ubuntu version, use this instructions.
First add the xbmc-svn to the opened file:
$ vi /etc/apt/sources.list.d/xbmc.list.list
And add in this file the following lines for Ubuntu 10.04:
deb http://ppa.launchpad.net/team-xbmc-svn/ppa/ubuntu lucid main
deb-src http://ppa.launchpad.net/team-xbmc-svn/ppa/ubuntu lucid main
To install XBMC do the following:
$ sudo apt-get update
$ sudo apt-get install xbmc