Screw furring strips to the interior faces of the wall studs if you are planning to install vertically oriented pine boards. If you are intending to install the pine boards horizontally, you can nail them directly to the studs. Attach horizontal furring strips at 24-inch vertical intervals by putting in 2-inch-long screws wherever a furring strip crosses a stud.
Place a pine board vertically in one corner of the cabin, with its groove facing the corner. Nail the board to the furring strips by placing a finish nail at each furring strip vertically along the side of the board in the corner. Nail the other side of the board by driving nails in at a 45-degree angle through the shoulder of the tongue.
Place another board on the wall so that its groove interlocks with the tongue on the first board. Nail this board through the shoulder of the tongue in the same way that you did the first board. This board and the remainder of the boards don't need to be nailed on the side with the groove, because that side will be held against the wall by the tongue of the previous board.
Continue to install boards across the width of the wall, cutting boards to fit around features such as windows and doors.