Find and mark each stud in the wall, using your electronic studfinder.
Use your level to draw horizontal level lines spanning the whole width of the wall, with one line two feet up from the floor and additional lines every two feet higher up the whole wall.
Install furring strips on the lines, using your nailgun to shoot two nails through the boards at each point where they cross a stud. In addition to putting strips all along the lines, put one along the bottom of the floor, and one along the top.
Measure the height of the wall, and cut your first plank to size on your miter saw. Stand it up at one end of the wall, using your level to make sure it's straight up and down.
(If the corner that it's standing against isn't straight, make the board straight anyway, leaving a gap at part of the corner; it will be covered by trim).
Secure the board by shooting two nails through the face at each point where it crosses a furring strip, including the very top and very bottom.
Measure and cut additional planks, locking them together by their long tongue-and-groove edges and nailing them to the furring strips. Cut the final strip lengthwise on a table saw, if necessary, to get it to fit.
Install trim around the floor, ceiling and corners to cover the edges of the boards.