Go read it in 'the guide' ya lazy bastid !
Its only been described here 2000 times !
Viet.... anytime you have a question... try and use the 'search' feature above before you ask ... most of the questions have been answered many many many times.
That one is also in 'Freds guide'.... you do know where that is right ? (you are not a rookie here)... under 'resources-articles' above ...