Update Jenkins from a war file

I have a machine with Ubuntu 12.04 and have installed Jenkins ver. 1.424.6 using apt-get based on *[this guide*][1], but there is a new version: New version of Jenkins (1.447.2) is available for download (changelog). If I press download, I get a `jenkins.war` file... but how do I use that for upgrading my current installation? or is that not possible before the apt repositories gets updated? [1]: http://www.mabishu.com/blog/2012/04/17/setting-up-jenkins-in-ubuntu-precise-12-04-for-php-projects/