Measure and draw your holes on the steel. A permanent marker works well for this purpose, just remember to cut on the outside of the marker lines to prevent them from showing on your finished product.
Put on your safety gear. Goggles, gloves, a mask and an apron should be worn at minimum.
Hold the oxy-acetylene torch away from you, with the flame adjustment valve turned off. Slowly turn the valve on the fuel tank 1/8 turn to the left. This should remain below 15 lbs. of pressure at all times. Turn the flame adjustment valve on the torch until the flame is approximately 1/2-inch long.
Open the oxygen to between 20 lbs. and 30 lbs. of pressure. Open the oxygen adjustment valve on the torch.
Brush the flame against a 2-inch to 3-inch section of the marked area until you see the metal begin to melt and be blown away. Continue heating a few inches at a time and cutting until the holes are cut completely.