head to the Temple in North Qeynos, just north of the Palace. Outside you'll find someone called Aurora something-or-another (sorry, can't remember her name). She gives you the quest; you might want to be lvl 19 before you try it solo, however- or take some friends with you. Its not too hard, but the first part is difficult soloing.
When you've done the first part, you'll have to head back to Aurora for the instanced second part. For the second part don't worry too much about the constructs; you only need to kill the named character (who is blue to you at lvl 19) to complete the quest.