start fire
douse fire
fuel fire
cook MEAT

To build a campfire, you must first gather firewood and drop it somewhere outdoors. You can then use flint and steel to start fire, creating a campfire. You may need to add more firewood occasionally, to keep it going, with the fuel fire command.

If you have fish, or a limb rent from a corpse, you can cook MEAT to throw it on the fire, and let the flames do all the work. To acquire food, you can rend a limb from a corpse or use a fishing rod to fish in a pond.