First things first. You will need to have advanced far enough into the game to unlock the character Aubergine. Which means beating the 2nd boss, Vespula. Which in itself isn't easy.
Once you have unlocked Aunergine, select her for the next mission; Zone 3 - Access Control Corridor.
Switch to your secondary weapon using
and fire the Singularity. Quickly switch back to your Helo weapon and gently press the
to use it to kill an enemy trapped in the Singularity. May take a few tries, as the Helo blade is pressure sensitive with the trigger. Otherwise it's easy enough.