To use them, you'll need to press and hold the Fn key on your keyboard, which will make the F keys appear in the Touch Bar. From there, you can select the key for the desired function.

The function keys on your keyboard are the most powerful computer tools that you're not using. We're going to fix that.

I'd like to be able to use my function keys without needing the "fn" key itself when I'm bootcamp-booted into Windows. Any ideas?

Function keys that enable convenient features like instant browser refreshing or screenshotting pages are lost unless you hold down the “fn” key on your keyboard.