I didn't know you were talking about bullets. That is a different ballgame.

Here are two articles that should help.
How to control bullets in Ribbon Versions of Word by Shauna Kelly
How to create numbered headings or outline numbering in Ribbon Versions of Word by Shauna Kelly

I believe they give step-by-step instructions. You do have to do all of the steps.

As for existing documents, there is no quick fix.