How can I update my iPhone 7

iPhone 7 Plus can be updated to iOS 15.7.3

If you are on iOS 13, you may need to update from a computer, as there may be some challenges with skipping a version when updating over the air. See link at the bottom of the answer.

You can check your current version here:

Settings → General → About

You can download and install software updates here:

Settings → General → Software Update

Remember to connect to Wi-Fi and a charger.

Your iPhone must have more than 50% power to update without a charger connected.

You can find more useful information here:

Update your iPhone or iPad - Apple Support

If your iPhone or iPad won't update – Apple Support (UK)

If you want to update your iPhone via a PC or Mac, see here:

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

• PC (iTunes): Update your iPhone, iPad, or iPod touch with iTunes - Apple Support