When you accept a quest, press the “Q” button to display the Quest window.  You can click the green link that appears next to your quest to automatically go to the quest NPC.

To find the location of an NPC or monster you can click the Folder button on the right side of your screen.You can also click a location on the Map to automatically travel there.

You can also use the Quest Track window located on the right side of your screen to help you find NPCs and complete your quests!