How to Update Your iPhone iOS

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

Did you know that most issues with your iPhone can me fixed with a simple software update? Updating your iPhone software can improve performance, add great new features, fix bug issues and ensure your device is secure. The link above will show you how to update your iPhone or iPad over Wi-fi or through iTunes. It is recommended that you back up any personal data that is important before a software update, to learn more about backing up your iPhone you can refer to this article How to Back up Your iPhone (Personal Data).