First you need to Purchase the Shockwave ability from an upgrade terminal, you can purchase this from the first upgrade terminal, it will cost you 1000 Credits. Once you have the ability you have to Hold RB and Press A this will unleash a deadly shockwave sending enemies in close range up in the air, you will see what enemies are in the air by the electrical bolt attached to them. The smaller enemies wont require you to shoot them while they are in the air because the shock slowly kills them, however the bigger enemies will need damaging in order to destroy them in the air. Simply repeat a number of times throughout the campaign and you will get this in no time. Hope This Helps.