How do I update my iPhone 7 to latest iOS update?

You can update an iPhone 7 to the latest release of iOS 15 – currently iOS 15.8.3.

About iOS 15 Updates - Apple Support

Update your iPhone or iPad - Apple Support

Updating iOS: common issues and solutions - Apple Community

You cannot update an iPhone 7 to iOS 16 or higher.

Your iPhone 7 is on it's latest available update (iOS 15).

You will not be able to update to the latest iOS (iOS 18).

Only the following models support iOS 18:

iPhone models compatible with iOS 18 - Apple Support (SG)