To enable the setting you must go into "Options" and select "Controls". There you will have to set the 7th line reading "Control turret in zoom" to "Yes"! Now apply the settings by pressing
I recommend doing the training mission on training difficulty. Advance to the part where you have to use the FLIR to dispatch the enemy infantry after destroying the three vehicles in the village. Switch to an external view, do not use FLIR do dispatch the infantry. Instead hover quite low and zoom in using
. Now you can control your turret with
. You will see a small dotted crosshair moving around. Use this to kill at least five soldiers in the village and the achievement is yours.
Should you have trouble making out the soldiers then I recommend switching to FLIR once in a while to see where they are hiding. Use auto-hover to hover in one place and remember to un-zoom to adjust your heading once in a while to face the enemies.Review 23 September 2014: Added button icon.