This has got to be one of the toughest questions you've asked. Snort is not an easy thing to manage. The first book I ever saw on it was several years ago at a Barnes and Noble bookstore. It was easily over 600 pages.
I checked your link, but I don't speak French. The snort documents page is here
. There's a link to a pdf of the Snort user's manual, which is "only"
238 pages! The user translated guides are here
. I would start with the French – Snort Installation Guide (pdf)
Actually, I'm getting a 403 Forbidden on that pdf link. You may want to email the author, Fathi Ben Nasr, (his email address is adjacent the link on the user translated guides page) and find out how to get access to the pdf link.