Updating your Apple's software is easy. Simply follow the step below.
Update Your iPhone, iPad or iPod
To update your device you should be connected to the Internet. Most recommend is WiFi.
- Go to Settings > General > Software Update.
- Then iOS will automatically check for available updates. Available updates download automatically if your device is connected to WiFi.
- But in some case if your are using VPN or proxy connections, they may prevent your device from contacting the iOS update servers. So for that if an update is available you can tap Download to download the update.
- After the download is completed tap Install to update your iOS.
So you are done :) . Enjoy it.
Source : Apple's Official Website