Speak with Muren Stormpike.
Hello, warrior! You show a lot of promise, but you still need to learn some tricks and Muren Stormpike is just the dwarf to teach you.
You can find Muren at the Hall of Arms in the Military Ward of Ironforge. Talk to him when you're ready to learn what it is to be a warrior.
Did you make the switch?
Ah, <name>. I heard the warriors of Dun Morogh bouncing your name around. I hope you haven't spent all your time in the breweries!