Measure the wall you’re going to install the backer board on. Mark the outline of the area with chalk.
Apply the wall adhesive to the wall you’re going to hang the backer board on. Apply a ½-inch to ¼-inch layer of the adhesive. Use the notched side of the trowel to make lines in the adhesive.
Place the backer board against the adhesive and press it in place. Leave a 1/8 inch between each section of backer board.
Drill screws into the perimeter of the backer board, spaced about 6 to 8 inches apart. Place the screws into the backer board ½ inch from the edge.
Fill in the joints around each piece of backer board with wall adhesive. Use the flat side of the trowel to smooth it out 1½ inches on the sides of each joint.