page setup

both are document-wide settings, so you do not need to select text first — margins and hyphenation apply to the whole document (or, if it already has multiple sections, to whichever section the cursor is in, which is why Ctrl+A first guarantees every section is covered). Do this before the table of contents so page numbers in the TOC are correct: margins change how much text fits per page, which shifts every page number after that point, and a TOC built before that shift would show numbers that are now wrong until refreshed again.