The key for numbering is the fourth link JimP gave you.
How to create numbered headings or outline numbering in Ribbon Versions of Word by Shauna Kelly
I note you are using the 64-bit version of Word. There is no reason to use the 64-bit version of Word, PowerPoint, Excel, or OneNote. There can be disadvantages in these programs.
High-power users of Excel or Access will benefit from the 64-bit version.