Today, eager Windows Phone enthusiasts will be able to get their hands on the latest version of the OS, Windows Phone 8.1, as Microsoft begins its rollout through the Preview for Developers program.
The Windows Phone Preview for Developers program gives registered users early access to Windows Phone updates, before it passes through the carriers' lengthy approval processes. This means you won't see any carrier optimizations in the update, or the latest firmware updates from manufacturers, but you will get the full, final version of the OS ahead of its wide release.
Windows Phone 8.1 brings several huge features to the platform, including Microsoft's homegrown Cortana personal assistant, the Action Center which combines notifications and setting toggles into a pull-down menu, custom Live Tile backgrounds, new lockscreens, and many more improvements.
The update is compatible with all existing Windows Phone 8 hardware, and the Preview for Developers should work on your handset without any major issues. Whether or not the OS finds its way to your device without the program is another story, as some carriers and OEMs may choose not to roll out the update; one example being the Nokia Lumia 810 on T-Mobile.
To get Windows Phone 8.1 on your device through the Preview for Developers, you'll need to register for the Windows Phone App Studio using your Microsoft account. After that, hop onto your Windows Phone and download the Preview for Developers app from the Store. When these two things have been completed, several over-the-air updates will bring you up to Windows Phone 8.1 in no time.
https://www.techspot.com/news/56379-microsoft-releases-windows-phone-81-preview-for-developers.html
I dunno what to do 
