How do i find out my friend code for animal crossing wild world on nintendo ds !?

write well im really having troubles with please please help! ive loaded the game up as normal then i go to the main gates and go to booker (i think it is ) and ask for my friend code and it says no essable point so i go into my connections and go on connection 1 ,2 or 3 and it says i still cant get it ! i have a sky box so it should work!? please help x :)