The , released in 2013, has a final supported software version of iOS 10.3.3 . Because it uses a 32-bit A6 processor, it is technically unable to run iOS 11 or any subsequent 64-bit operating systems. How to Update Your iPhone 5c Software

This is the most direct way to download the software update directly to your phone:

How to update an iPhone 5c to iOS 13? - Apple Support Community

If your device is not yet on iOS 10.3.3, you can download the final update using these two primary methods: