I've found how the update can be done manually: http://vortexbox.org/threads/3619-Bliss-Version-Update
With a little bit more explaination:
When you visit the download page, you will see a package for Vortexbox. Click on it.
http://www.blisshq.com/download.html
On the following page you see the download link.
http://www.blisshq.com/downloads/rpm/noarch/bliss-20120403-1.noarch.rpm
With the command "wget" you can download files via commandline. So type in to the CLI
wget http://www.blisshq.com/downloads/rpm/noarch/bliss-20120403-1.noarch.rpm
With yum localinstall you can install downloaded rpm files
yum localinstall bliss-20120403-1.noarch.rpm