Welcome to Flyertalk and to the wonderful world of frequent flyer programs
Now that you joined Flying Blue and as you need to "learn" the rules, in addition to AF/KL and FB web sites, you can have a look (and participate ) to the FB forum and its sub-forums AF&KL of Flyertalk.

Everytime you fly a Skyteam airline or another airline being a FB partner, be sure to enter your FB# in the booking. If you don't do it, you can still do it until check-in either on-line or at the airport.