Clear everything out of the closet, including any hardware. Use a screwdriver to remove any hooks and remove the closet rod hanging hardware. Leave the switch plates intact since raising the plate by over 1/4-inch will keep the screws from reaching the electrical box.
Measure the height and width of each of the walls that you plan on covering with cedar using a tape measure. Multiply the measurements together to reach the square footage of the walls and add the totals together to reach the total area. Use this number to purchase the correct amount of cedar planks.
Use a stud finder to locate the studs in the walls of the closet and mark them with a pencil. Alternatively, you can pound a thin nail into the walls at progressive intervals to find the studs.
Apply a bead of construction adhesive to the back of the first board in a continuous s-pattern. Set the board in place at the back of the closet at the bottom of the wall. Keep the groove side up. Use a nail gun to nail the board to the studs along the top edge of the board. Make sure the cedar is level before nailing. Fit the next board and glue and nail into place. Finish one row at a time and keep the seams alternating.
Finish one wall at a time, cutting, gluing and nailing the cedar planks in place until you finish covering the walls.
Install the hardware previously removed, predrilling pilot holes into the cedar before anchoring screws into the wall. Reinstall the clothes rod and hang up your clothing.