This achievement will be picked up right at the start of the game during the tutorial level. You start the level in a mine where you will be taught how to shoot. Once you leave the mine it will ask you to cut down some tree's and cars so you can craft a gun. The next part of the mission will take you to a base you need to defend by killing a few husks. Once you completely defend the base your achievement will pop.
If you would like to see a video for this achievement, I will leave mine below.