After accepting this mission, either go to the city teleporter to transport to the city, or walk the short distance.
In the section that is highlighted on your map, locate the large turrets, usually located along side of the buildings. If nothing pops up right away, someone has already beaten you to that turret. You can wait for it to be available again, or simply find another turret to update. Clues that a turret needs updating is by the Deferi NPC saying, "This turret is useless! I need this turret updated!" and the Borg people that are attacking it are only being damaged by 1 hit point by the turret's firing. When this happens, go up to the turret and quickly press the button that will appear that says "Update Sofware Modulation". Repeat this process 10 times and return to the City mission giver.
If the turret is already updated, the Deferi NPC would say, "Take that Borg!" or "The turret's software has been upgraded." and the Borg people that are attacking it are being damaged as normal and die.