You must first use the incense on the ground in front of the NPC by clicking on it. (As a future suggestion, look up quests on WoWhead rather than WoWpedia, as the former is often more detailed).
After using the incense, you will be transported to a different "phase" of Darkshore, and there will be a Thistlebear, Stag, and Moonsaber spirit. You get to pick one spirit to get a "blessing", which affects the rest of your time in darkshore. The Stag is a 10% move speed bonus. The Moonsaber is 10% haste. The bear is 10% less damage taken.
This bonus is nice, but restricted to Darkshore, so don't fret overmuch on a "right" choice. You can only get one. After doing so, you can speak to the Furbolg nearby to complete the quest and receive your reward.