How can I update my iPhone 7

To update your phone, select Settings > General > Software Update. If your iPhone is eligible for an update, you will be prompted to do so. You iPhone 7 should be able to update to 15.7.3. You can find more information here:

Update your iPhone or iPad - Apple Support

An iPhone 7 isn't capable of 16 or above; they require an A11 or better CPU. To install 15.7.3, use a computer or the Software Update function in Settings.

(234928)