How do I get my IPhone to update now and not tonight?

You can manually update by going Settings>General>Software Update and tapping on Install Now.

~Lyssa

You can update through iTunes on a computer. You can download iTunes from Apple website and install on computer then connect the phone to the computer and you can install the update immediately.

Update to the latest version of iTunes

https://support.apple.com/en-us/HT201352

Update your iPhone, iPad, or iPod touch

https://support.apple.com/en-us/HT204204