how to update clamav / clamtk virus definition?

Hi,

I'm a totally noob *nix user and I'm totally lost : hos do I update de virus definition?

I've read about script located in

but ... I don't find this path :/

when *I try to run it ask me tu create a config file

and when I run clamtk, it tell me that my virus def. is outadted but it do not update it...



so I'm lost, sorry for asking your help (and sorry for my bad english wich is not my natural laguage)