I want to update the software

Update your iPhone, iPad, or iPod touch

1. Plug your device into power and connect to the Internet with Wi-Fi.
2. Tap Settings > General > Software Update.
3. Tap Download and Install. If a message asks to temporarily remove apps because iOS needs more space for the update, tap Continue or Cancel. ...
4. To update now, tap Install. ...
5. If asked, enter your passcode.

Update your iPhone, iPad, or iPod touch - Apple Support

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

See here: Update your iPhone, iPad, or iPod touch - Apple Support