Setting up the numbering:
How to create numbered headings or outline numbering in Ribbon Versions of Word by Shauna Kelly

Inserting Cross Reference:
Complex Documents - Cross-References




Word is a powerful program, but it does not include mind-reading artificial intelligence! When you want a cross-reference that can automatically update, Word needs a way to indentify what it is you want to reference. The built-in heading styles, numbering and bookmarks are all ways that Word can figure this out.