Remove the 2 plastic caps from the mounting bracket access holes.
Drive a 20 mm wood screw (longer screw) through the mounting bracket and into the cabinet side.
If the provided 20 mm screws are not long enough to secure the dishwasher to the cabinet side, use screws that are long enough to secure to the cabinets.
If you have framed cabinets, use screws that are long enough to secure the dishwasher to the cabinets or attach wood spacers (not included) to the cabinets on either side of the dishwasher.
Reinstall the plastic caps.