Simply let a pot with some food in it bowl over & it will go on fire and then grab the red fire extinguisher, press A to pick it up and X when near the fire to extinguish it.
Easiest done on level 1-1, chop an onion or tomato, pop into the pot. Wait a few seconds until it cooked, wait a little longer so it boils over and goes on fire, then extinguish it.
I think this is just going to happen naturally for most people as its easy to forget about a pot and then have a fire when you are under pressure.