Newbe question.
Good morning: I read the doc's last week and I think I might be missing something. How do I start?  Do I have to turn on some feature in my sitemap.xmap?  Can I just put an libre.xml file in a directory if so which one?  I understand the concept on how to write the file but I don't know where to put the file or what comments I must make to activate it.  Any help would be great. 
Thanks so much.