Twitter question!? Please help im new at Twitter!?

[bellaa_smiley]

Ok so to be honest im really trying to Twitter Justin Bieber lol so how do i like write on his wall thingy? People say to Direct Message him and i know where direct message is but when it says send to whom? It wont show his name.
I've tried that Charlott and after I'd sent it i didn't see it on his wall ... :/
why can't i see the post i sent him on his wall?

[Charlotte]

You have to put (in your status box thing) @(JustinBieber'sTwitterNameHere) and then write your message.

[Marylou]

Follow Him First ,
than On Your Twitter Put
@justinbieber Than Your Messege
He Might Read & Reply But Alot Of People Send Him A Tweet
so Dont Get Your Hopes To Up,,
Folloow Me (:
JusstMaryloou7