According to the National Fire Protection Association, here are the steps to take:
Pull the pin.
Aim low, pointing the nozzle at the base of the fire.
*Note: Do not touch the plastic discharge horn on CO2 extinguishers. It gets very cold and may damage skin.
Squeeze the handle to release the extinguishing agent.
Sweep from side to side at the base of the fire, until it appears to be out.
Watch the area. If the fire re-ignites, repeat steps 2-4.
If you need help after a fire, call the professionals at ServiceMaster of Tacoma, 800-339-5720