Find and mark all the joists in the ceiling, using an electronic stud finder, level and pencil.
Measure the ceiling length along the edge of the ceiling where you want to start the courses of planks, running perpendicular to the joists.
Mark out the measurement to a wood ceiling plank. Cut the plank to size on a miter saw.
Hold the board to the edge of the ceiling, with the groove side facing the wall. Leave a 1/2-inch space between the board and the wall. Drive nails through the face of the board at each point where the board crosses a joist, using your trim nail gun. Place two nails per joist.
Cut the next board to the first size. Press the grooved side of the board to the tongue side of the first board. Get them snug to each other. Shoot nails up through the sides of the second board (not the face), putting one nail per joist.
Repeat for each board, building your way across the ceiling. Use a table saw to cut the last board along its length, so it fits against the far wall with a 1/2-inch gap there. Ceiling trim will cover the gaps.