How To Write To Certain Person C O On Letter . How to address a letter: Write the address on the front of the envelope in clear, all capital letters and using a pen or permanent marker. How to Address Envelopes in Care Of 11 Steps (with Pictures) from www.wikihow.com The first paragraph (opening) the first paragraph of formal letters should include an introduction to the purpose of the letter. Enclose all forms and information required to meet the request. To write an effective authorization letter, we have to pay attention to the following points :