Instructions
Travel to a major city, such as Stormwind if you are Alliance or Orgrimmar if you are Horde.
Travel to the mining trainer. Near this trainer will always be a forge.
Stand next to the forge.
Press "P" to open your abilities book.
Click the "Smelting" icon.
Click "Smelt Copper."
Click "Create." One copper ore will make one copper bar, which is automatically added to your inventory.