Software updates

Hello mugdha,

First make sure you are following the correct procedure as outlined in this article: Update your iPhone, iPad, or iPod touch - Apple Support

If that doesn't work then here are articles for troubleshooting:

If you can't update or restore your iPhone, iPad, or iPod touch - Apple Support

If your iPhone, iPad or iPod touch won’t update - Apple Support

It would also help to have more details as to what messages you are seeing when it won't update, or at what stage in the process it is failing.

Make sure your device is connected to WiFi (not a hotspot) and plugged in. Then head to Software Update and choose download and install or install now (whichever is present).