Copper is a versatile metal which reacts by wearing and in air. It will get a patina that makes it to a personal and unique piece of jewelery day by day.
If you want to get the shiny, smooth surface of your new copper jewelery you can wash in warm soapy water and dry with a soft cloth and polish it occasionally.
If you are not wearing the jewelry, put it in a plastic bag to protect it from tarnishing. If your copper jewelry has already tarnished, you can use to clean it following methods:
Use salt and vinegar combination to reduce the oxidation of the copper. Give pure vinegar and salt over the copper and then wipe it well to remove the patina and dirt. Then rinse with water and polish with a soft cloth.
The other option is the use of citric acid. Cut a lemon in half and sprinkle a half with salt. Thus rubbing off the piece of jewelry until the surface shines again. Then rinse with water and polish with a soft cloth.