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*, 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?