After you’ve arranged everything to your liking (don’t forget to save often, like a paranoid squirrel with acorns), click the Save Menu button. That big blue button is your best friend.
Now, go check your website. Hover over the parent menu item. If you see a little cascade of options appear, congratulations! You’re officially a dropdown wizard.
If nothing happens? Don’t panic. Your theme might not support dropdowns automatically. But that’s a rare hiccup—most modern themes do.