To use carbon paper sheets you quite simply place it between 2 sheets of paper. Then by writing firmly on the top sheet with a pen or pencil the ink from the carbon paper sheets or sheet is deposited on the paper underneath. As a guide, this technique is usually limited to 4 or 5 copies per carbon paper sheet.
Carbon paper has mostly been superseded these days by electronic means such as a photocopier, though it is still used for making copies when using a typewriter. Also, a carbonless copy paper is used where instant copies of documents are needed like when filling out an order request, or customer invoice pad.