The app updates automatically to the newest version. Users are somewhat notified in the sense that the `Downloads` tab opens up in the background and if you navigate to it you'll see that a game was recently updated :)
We recommend using https://itch.io/docs/butler/ to upload all game builds. It allows users of the app to download small patches instead of re-downloading the full game. And it lets you push updates faster, since it only uploads what changed since the last build!
It's a command-line tool, which some folks don't want to get into, but I promise it's really easy to set up and get your first push going, and I'm planning on integrating into the app so you can just drag & drop folders to push a new version :)