Instructions
Play "Harry Potter and the Order of the Phoenix" until you reach the point where you must enter Moaning Mrytle's bathroom. All the torches in the bathroom are unlit, so you need to cast Incendio to light them so you can see.
In "Harry Potter and the Half Blood Prince," play until you reach the point where Nearly Headless Nick guides you to the boathouse to meet Luna. Here, you need to cast Incendio to light the fireworks.
Point your Wii Mote at the TV and the Wii Sensor.
Press the "Up" and "Down" arrows repeatedly to cast the "Incendio" spell. "Up," "Down," "Up," "Down."