Write their house number and street address on the line below it. Then write the city, state, and zip code on the line under it.Put your name and address, the "return address", in the upper left corner of the envelope. The importance of letters of instruction can't be understated. Our free templates and this guide can help you get started. There are five required parts of a letter and one optional part. The five include a heading, greeting, body, closing, and signature. Greeting: Start with a friendly salutation. In the following letter, Isabelle Graw shares her reflections on the impact of the Trump regime and neoliberal policies on the art world. Learn how to write a letter to a friend in 10 easy steps with examples.