Software update

See this Apple article: If your iPhone, iPad or iPod touch won’t update

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

You can do the update via PC, See this Apple article: Update software on iPhone, iPad or iPod touch in iTunes on PC

Update software on iPhone, iPad or iPod touch in iTunes on PC – Apple Support (UK)

If you have a Mac see this Apple article: Update your iPhone, iPad, or iPod touch with the Finder

Update your iPhone, iPad, or iPod touch with the Finder - Apple Support

From the screenshot in one of your other posts:

Do you get any error messages?

Tell us.

I am using iphone 12 mini. When i open software update option, download and install option is not checked and not active. I am unable to click it. Please help