In order to update your OS in Mudita Pure, you ought to do it via Mudita Center.
After installing the program, please follow the instructions below.

You can find the download link for all operating systems here: 
Download Mudita Center

1. Connect your Mudita Pure to your computer with a dedicated USB cable and make sure that Mudita Center runs on your machine and recognizes your device.

2. Go to the “Overview” section inside Mudita Center.

3. In the sub-section showing your Mudita OS-P (Mudita OS-Pure) version, you will be notified whether your phone needs updating with an “Update is available” prompt.

4. Click the “Download Now” button and follow the instructions.

5. After a successful update, your Pure will automatically restart. After that, you will be able to see your Mudita OS-P (Mudita OS-Pure) version in the “Overview” section.

Note: Remember to not use nor unplug your Pure from the computer during the update process.