In order to obtain this achievement, you need to put at least one point into the exploration tree that is located in your talents. For ease, when you begin the game you can simply put one point in exploration. After you have put one point in the tree, you can now skin creatures by running over their corpses and pressing the x button. Here is a picture of where the skill is located:
I personally find this achievement easier to obtain if you go into the sewer system and kill the creatures there. When you leave the area and come back, the creatures respawn and you can do it until the achievement unlocks.
I hope this helps! Let me know if there is any way I can improve this guide, after downvoting so that I can maybe improve the guide. Thanks and good luck!
