First of all you will have to remove previously installed brackets or shelves from your wooden closet. Use screw driver to remove the closet rod and all other wooden screws attached to the closet. Now you will be able to take out shelves and brackets from the closet, put them on the floor after cleaning them with a cotton cloth.
Put drywall compound in holes in the drywall and use an iron scraper to smooth them. Give the compound about 12 hours to dry out completely or till its colour changes to white.
Decide the number of shelves you will need while keeping in mind the total height of the closet. As a rule of thumb, compartment should not be smaller than 15 inches, though you can go for 12 inch shelves too. The bottom shelf should be about 20 inches from the closet floor. Measure 20 inches with a measuring tape and mark the spot on the wall with a pencil.
Measure 15 inches from that spot upwards and mark another line, keep on going till you reach the top of the wooden closet.
Extend the line to three sides with the help of Set Square and use carpenter’s level to make sure that they all are aligned. Place the wooden board on these marking and screw it to the closet wall with the help of nail gun or wooden screws and a screw driver.
Measure the width and length of your closet in case you have to make more shelves, and use saw to cut plywood into square boards required for the shelves.