How to back up iPhone 5s with a broken screen?

I dropped my iPhone 5s and broke it badly, I can't use it anymore I can't swipe, or type. I really want to back it up to iTunes but I need to ''respond to my iphone'' but I obviously can't. I can't use siri because it says I have no internet connection (but I should) Please help! How to back up iPhone 5s with a broken screen

Sync it with your computer -- no response needed