I have found it difficult to find the line what exactly the line is that I need add to my
/etc/apt/sources.list ... I finally found it on the Google site here.
But to spell it out:
# Google software repository
deb http://dl.google.com/linux/deb/ stable non-free main
If you are using the GUI, you can simply go to
Software Sources > Other Software > Add
and add the repositories this way. This should then also automatically provoke an update of the software sources...
There might get a warning saying that the package is unsigned. I haven't tried, but from what I can see, there is a link on the Google page.