Measure the open basement ceiling from the wall where you are going to start the courses of ceiling boards. (Note: You must start along a wall that runs perpendicular to the joists.) Transfer the measurement to a ceiling board.
Use your miter saw to cut the plank to that length, at 90 degrees (straight across).
Hold the board to the basement ceiling, setting the grooved side toward the wall and sitting half an inch out from it. Secure the board to the joists by shooting the nails from your nail gun straight up through board. Put two nails at each point where the board crosses a joist.
Measure and cut the next ceiling board to size. Lock it in along the side of the first board. Secure it by shooting a nail through the side of the board, at an inward angle, at each point where it crosses a joist.
Continue cutting and hanging the boards, working out across the basement ceiling. Use a table saw to length-cut the last board so it fits along the ending wall with a half-inch gap there. Your ceiling trim will hide the gaps.