go to your post, and under your category section choose your category. If the category doesn’t show then it does’t exist. Afterv selecting the category go to posts/categories and see if it is there, and if it’s not, then add the category. Then go to your post and choose the category
2) from appearances/menu, under Theme location, your menu should be the primary menu. At the bottom of the page where ‘categories’ is places, if you see your category, then click ‘add to menu’ and save menu. Now your category has been added as a page in your menu.