[TYPO3-english] what is the right way to include css files in typo3 v4.5 with extbase

[Calgacus map Brude]

Hi,
Sorry for such a newbie question but I've seen  few examples that look different to me  and I didn't fully understand them anyway.  Is there a good piece of documentation I just didn't find yet?
I am trying to make some extbase extensions in typo3 v4.5.   I just assume I should link my css files and have them as part of my extension under a Public/Css folder but then how do I link it (as in uase the css in a web page),  it seems like a complex of config options in setup and contants.

I was looking at this snippet :
http://typo3.org/documentation/snippets/sd/278/
and it seems to relate but I don't even know where I would include the snippet, what file of mine should I copy that into? a domin, a controller?  

Thanks