Once you reach 19th you will automatically get a hallmark quest in your journal which tells you who to talk to. I would wait until 19th before doing the quest personally.
u can also do this before u reach lvl 19. Did my at 18 in freeport, but kinda disapointed on the difuculty of the quest. as u pretty much choud solo it whit one eye closed. In freepoort at least talk to the guy that u did the priest lvl 10 quest from he gives u a hint to who to seek out.