How do you use that Sonic Blade?

[Guernsey]

Exactly as the title says, how do you use that blasted sonic blade?

 

[DiceKiller]

When you've obtained it and have it equipped, it should show up in the 4th slot of the command menu when it's available to use. When it shows up, go to that slot and press X. You press X every time it lights up again afterwards