At lvl 66 horde, how do I get to vashj'ir from orgrimmar? I hear theres a quest I get.. or must I lvl higher?

You're not high enough you need more lvl, you should go to outlands until you're 68 or 69, than take the zeplin to howling fjord or borean tundra (Northrend). Vash'jir is for levels 79 or 80.