During the beginning of final mission youre tasked with finding ammo for a machine gun. Youre told to check a tank. Upon taking ammo to the MG your character asks about a repair kit. The machine gunners tell you to check a gun in the center. This is the gun you must repair. Shortly after civilians will enter the map and their car will break down, you must than steal their repair kit. Make a save as you only have one and use it on the gun to get the achievement than reload the save as the tank is more useful.