First things first, please make sure you have “Preview for developers app” still installed and you are signed in and have enabled it for receiving updates. If not, you may not get any “update available” prompt when checking for update.
Now go to Settings—>Phone update—> check for updates. Once prompted let it download the update. 8.10.12393.890 update is about 21 MB in size and the whole installation experience takes 15-20 minutes including data restore post update. Once the update is done you will be informed. Check the above screenshots.
Changelog & what hasn’t changed:
- There are some reports of change in phone boot-up animation and quiet hours being available without Cortana, both of which doesn’t look valid and I couldn’t see any changes here.
- There are no visible changes or new features which I could find
- The home-screen to app and app to home-screen transition times look faster
- Some bugs related to notification center have been fixed and it really works smoother even when you have lots of notifications
So, it mostly looks like bug-fixes and performance improvements kind of update. We will keep on checking and you also do the same and share if you see anything fancy!