To get this achievement, you will need to hit an animal from at least 100 meters away. Most rifle scopes are zeroed to 100 or 150 meters by default and should be relatively easy to hit.
If you are unsure about the distance to an animal and have not unlocked a rangefinder, you can use the in-game map to approximate the distance. After spotting an animal with the binoculars, the animal will appear on the map. From the map screen you can see the distance from yourself to the target animal.