Wait for the stove to cool if it was used recently. Do not attempt repairs of any kind on the stove when it is hot or was recently in use.
Turn off the gas supply to the stove.
Pull off the stove's cooled burner grates, and set them aside
Lift the stove's top panel. It is the section from which you just removed the burner grates. Lifting the top panel exposes the pressure regulator. You will see a screw with a slot in it under the top panel.
Turn the pressure regulator screw clockwise with a screwdriver to lower the pressure and to lower the flames when the stove operates, or turn the screw counterclockwise to raise the pressure and raise the flames when the stove operates.
Lower the stove's top panel to its normal position, and replace the burner grates. Turn on the gas supply. Light the stove to ensure its pressure is at the correct setting.