Apple has begun rolling out iOS 12.1.3 to iPhone and iPad users. The update comes after its beta process which began in December of last year. Now, the software should be available for anyone who checks for updates in the Settings app on their device. It focuses on bug fixes and security improvements under the hood.
You can read the release notes for iOS 12.1.3 below.
To install the update, head to Settings > General > Software Update. So long as the software has reached your device, you should see the option to download and install it. Be sure to have plenty of power left and a stable Wi-Fi connection to avoid any interruptions during the process.