Compatible devices are notified automatically about the iOS 11.2 update, but should that not happen for whatever reason it can be triggered manually by going to Settings – General – Software Update. Tip: iOS 11.0.3 is not part of Apple’s beta program (where iOS 11.1 is currently in testing), so if you are you will need to unroll your device for iOS 11.0.3 to show up.
Apple’s iOS 11.0.3 release notes list fixes for two specific problems:
Fixes an issue where audio and haptic feedback would not work on some iPhone 7 and iPhone 7 Plus devices
Addresses an issue where touch input was unresponsive on some iPhone 6s displays because they were not services with genuine Apple parts