How to Update Your iPhone October 31 2016
Make sure you're connected to the internet. Go to your Settings app, tap on General, then tap on Software Update. Your iPhone, or other Apple device will automatically search for any new operating system updates available. At the time of this blog post, iOS 10.1.1 is the latest version available, with subsequent updates being released in the coming weeks and months.
It's important to keep your device up to date because these updates include fixes for bugs as well as performance and security enhancements. Keep in mind that if you have an older device, a newer iOS version could slow it down, but that's mainly when jumping from iOS 8 to 9, or 9 to 10 (current).
Apple released an iOS update today, so get downloading if you haven't already.