How To Write An Address One Line . City/district, state line 4 : Write the street address or post office (p.o.) box number on the second line. Update Mailing Address on Murphy Online by Jan. 8 Newsroom from news.stthomas.edu What is the proper way to write an address? So every line will be separately. There are three ways to correctly display the return and/or recipient name field names if there's a partner or spouse.