Moving categories to Nav bar

I am thinking of slimming down my categories and adding them to the nav bar, with drop down lists for sub categories. I’ll have to go in and edit all my previous posts to slim down the categories (I think I was confusing them with tags when I started. lol) – Anyways my theme is liquorice and the site is thehealthycollective.com.
Do I do this by creating “pages”?