To craft a Clay Pot, you will need a Pottery Wheel, a Clay Shaper, and some Clay. Put the Clay in the Pottery wheel, the Clay Shaper in your inventory, and craft a Fresh Clay Pot on the Pottery Wheel. Next put the Fresh Clay Pot in a Campfire to fire the Clay Pot. Remember to quickly take the Clay Pot out of the fire after it's fired so the durability does not drop.
Now you can place the Clay Pot on the ground and put items in it. Or you can put Wet Clay Balls in it to preserve food. It is also placed in the campfire together with edible ingredients to cook meals.