Find the wood studs in the desired area near the bar using the stud finder. Mark the location of the studs on the wall using the pencil. Take a measurement of the distance from the center of one stud to the center of the next.
Place the bar shelf topside down on your working surface. Position the brackets on the shelf board the same distance apart as the measurement made for the wall studs. Mark the location of the bracket holes with a pencil. Pre-drill the bracket holes in the shelf board, using care to not break through the surface of the shelf. Attach the brackets with the 1/2 inch wood screws.
Position the wood trim board on the top side of the shelf board. Hold the trim board in place, and drill through the underside of the shelf board to pre-drill four evenly spaced holes along the length of the board. Attach the trim board to the top of the shelf board with 1-inch wood screws.
Place the assembled bar shelf unit against the desired section of wall and set the carpenter's level on top of the shelf. Adjust the position of the shelf until level. Mark the position of bracket holes with the pencil. Pre-drill the bracket holes in the wall, ensuring that the drill bit contacts and bites into the wood stud. Attach the shelf to the wall using long 1-1/2 inch to 2-inch wood screws.