Instructions
Press "Right" on the control pad while in wolf form to use Link's "Sense" ability. This will allow you to see the Poe and enter into combat with it. Poes will only appear at night time, except for when you are inside a dungeon or a cave.
Attack the Poe by using the "Z" button to lock onto the enemy and either swinging the Wii remote or pressing the "A" button to attack. Pressing the "A" button to do a diving jump attack is the easiest way to attack a Poe, as they can fly out of range from normal attacks.
Hit the Poe until it falls to the ground and a black orb rises out of it. Press the "Z" button to lock onto the orb and press the "A" button to leap onto the Poe and take its soul. You must do this before the black orb re-enters the Poe's body and brings it back to life.