Turn on the air conditioner. Set it to the temperature you want in the house or the rooms in which you plan to adjust the vents.
Position a ladder or chair carefully under the air vent. Be careful if you have to stand on furniture to reach the vent.
Look for a switch on the air conditioner vent.
Slide the switch to allow more air into the room, or slide it the other direction to lower the airflow into the room. Continue to slide the switch in this direction and the airflow will become closed off completely.
Readjust the switch as needed to get the desired air conditioning effect in the room.