The easiest way to get this achievement if you're just starting is to begin cutting down trees. Near the surface there will be an abundance of them. It takes 60 pieces of wood to make a full set of Wood armor (Helmet, Chest, and Leggings). Then simply move your Wood armor pieces over to the vanity slots since they will automatically equip in the armor slots. Once they're all there, it should pop up.
If you have already played a bit, then just move your armor over to the vanity slots. It does not have to be a matching set.