After placing the tile, players may place a meeple as a farmer on one of that tile's field segments. A farmer is placed "laying down".
Unlike highwaymen, knights, and monks that are all placed standing up, farmers are laid down on a tile because they are only scored at the end of the game. Consequently, they are not returned to your supply after scoring. Laying farmers down ensures that you remember to leave them on the board. As always, you can only place your farmer if there are no other farmers in the field.