i finally want to start using it, but the game doesnt appear to mention anywhere how to deploy it. what the ****am i missing?

Attach it to your weapon as an underbarrel attachment. Select left on the D-Pad on your Xbox controller, that will bring up an image of the "single shot" setting and there you go, fire away. Hologram Ahoy!

On another note, last night I managed to somehow head shot someone with the Hologram, the setting on my gun wouldn't change back to auto fire and I was spamming left on the D-pad and then someone dropped down in front of me, I hit fire, a hologram ran out and the guy dropped dead. No one else was around and I got the kill for it, but even afterwards my gun wouldn't change back to full-auto and I had to jump off of a building to get it to reset.