How To Write A Letter To A Possible Relative . Ensure to include a signature. Remember this is the first line of communication. how to write a sponsorship letter Sponsorship letter, Donation letter from www.pinterest.co.uk Then write the city, state, and zip code on the line under it. After reading this essay, students can try to write their own letter to a relative. The first step in addressing a letter to multiple people is determining whether you need to send your letter to multiple addresses and how to format your header.