This achievement seems a progressive one and it seems to come really early on, too. It's an easy one to get without focusing your attention on obtaining it. It'll just come.
When you use cameras throughout the missions to scout areas, allow the cursor of a camera you have hacked to hover over any enemies you see within that area and they become tagged so that once you exit the camera, you'll be able to see their location from where you are.
Let me know if I'm misinformed or inaccurate and I'll change what needs to be changed if needed.