Once you reach level 10, you'll be able to take on guildhests, these are basically small 'dungeons' to teach you how to use your class in instances (real dungeons). The first will simply teach you the basics, you'll get a team and take out about 15 enemies. They are all very simple and weak, so assuming you have a group who knows what their role is (i.e. tank, DPS and healing), there should be no issues with the trophy.
Complete 1,000 hests to earn another trophy.