Instructions
Equip the Crossblade by pressing the directional pad in the direction of the weapon's assigned slot. Look for the Crossblade in the on-screen directional pad and press the pad in the appropriate direction.
Press the Right Thumbstick to make a targeting reticule appear. Move the reticule over a torch, then move it to the object you want to attack with the imbued blade.
Press "R2" to throw the Crossblade. It will become imbued with flame from the torch, then the weapon will hit the second target.