Black Prince Help

Hi everyone, I'm looking information about how to start legendary quest to be able to buy stuff from the Black Prince quartermaster and don't know how to talk to them or something... i checked wowhead but the npc giver to start the quest isn't working here in warmane though, any advice, or a "where should I begin" will be appreciate.

So far I know where them are and also when I kill "Ancient mogu spirits" at "Tu Shen Burial Ground-Vale Of eternal Blossoms" i gain reputation with them

but although im at the moment friendly with them i can't speak with them or see what they sell...