Apple released the official version of iOS 13 on compatible iPhones on September 19th. Since then, we've seen two important updates – iOS 13.1, which, according to our count, introduced 22 new features, and iOS 13.2, which also added 22 new features. Today, on December 10, Apple introduced the third major update: iOS 13.3.
Version 13.3 went through four beta rounds of testing, following the same path as iOS 13.2. During this time, most of the new features and changes came with the first beta release. The following three updates showed at most one or two visible changes, with most appearing under the hood.
To update to iOS 13.3, open the Settings app On your iPhone, tap General -> Software Update. Follow the instructions on the screen to begin downloading the software to your device, then continue with the update. You can also just wait for it to install automatically when Automatic Updates is enabled.