can someone tell me how to get that ?
Challenger Firehun or Senior Sergeant Firehun or Champion of the Naaru 
i dont know so much about PVP

You get a titles is many different ways. One way is to have had a PvP title from pre-BC. Another is to get attuned for SSC/TK:the eye or from getting attuned for BT/Hyjal. The last way is to get very (VERY) good in arena, thus getting duelist, challenger, gladiator titles. None are easy to get (the 1st one is impossible if you didnt have a pre-BC character)

You get a titles is many different ways. One way is to have had a PvP title from pre-BC. Another is to get attuned for SSC/TK:the eye or from getting attuned for BT/Hyjal. The last way is to get very (VERY) good in arena, thus getting duelist, challenger, gladiator titles. None are easy to get (the 1st one is impossible if you didnt have a pre-BC character)