How do I update software on my iPhone 7 Plus?

The latest update for the iPhone 7 Plus is iOS 15.8.3

Tap Settings > General > Software Update on your phone.

The iPhone 7 Plus cannot update to iOS 16 or iOS 17......if that might be what you are asking.

Faisalsuwayl wrote:

Upgrade software

In the absence of any relevant information, please see: Update your iPhone, iPad, or iPod touch - Apple Support

And: If your iPhone, iPad, or iPod touch won't update - Apple Support If the above Apple articles do not help, please post back with relevant information.