I want to update my iOS

Update your iPhone, iPad, or iPod touch

• If you have an iPhone 5S or 6/6plus, the highest you can update to is 12.5.7

• If you have an iPhone 6S through 7, or SE 1st generation, you can update to 15.7.8

• If you have an iPhone 8 or higher, or SE 2nd or 3rd generation,you can update to 16.6

Go to Settings > General > Software Update.

This link will show you how to update your iPhone, iPad, or iPod touch using WiFi -

Update your iPhone or iPad - Apple Support

This link will show you how to update using your computer -

Update iOS on iPhone - Apple Support

Your tag line says "Phone 6s Plus, iOS 13."

If that is accurate, you can't install iOS 16.5.1 (the version mentioned in the Related Article). You can upgrade your phone from iOS 13 to iOS 15.7.8.