Finish enough missions that it will let you near it, then put Mutagel in your last hotbar slot. It shows you which part to use, a foot or the head, and that part throws sparks until the hack lands. A red circle appears around you when you start: keep the Stryder inside it for the whole hack. The hack itself is a rhythm game, and you have to hit every prompt in a row. One miss wipes all your progress and it fights back, and taking any damage yourself does the same, so clear the area before you begin.