To use this skill you need access to a fire (campfire, oven or even a forge). Double-click on a food item, then on the fire to try to cook it. Cooking skill also lets you try to combine certain objects to make baked goods.
Lockdowns:
Use water on flour to make dough.
Use dough with fruit, meat or vegetables to make a pie.
Use dough with honey to make sweet dough.
Use sweet dough and flour to make cake mix.
Use sweet dough and more honey to make cookie mix.
Secures:
If you use a bladed object on a caught fish, the Cooking skill will also allow you to bone and gut it into raw fish steaks.