UniFi firmware downloads are now available separate from the controller. You can find them within the release post in the blog section, or in the downloads section of our website. Firmware is also bundled with the controller.
After the software is installed, the controller will automatically check for updates. Because the UAPs will need to receive updates and reboot quickly, the controller allows the user to decide when to upgrade. Optionally, users can manually upgrade the software by saving a backup configuration file (Admin->Backup) and uninstalling the old software and then installing the new controller software, then uploading the previous backup file.
To sign up for beta, if you haven't already, you may follow this article.