MuseScore's desktop program will not work natively on Chrome OS, but there are some workaround solutions:
Alternatively, it is possible to install MuseScore's Android app on recent Chromebooks. You will need to update to the latest version of Chrome OS first. See the Chromebook support documentation for help installing Android apps on Chromebooks, and a list of supported devices. The app only supports playback of existing scores, not score editing or creation, but you can sign-in to your MuseScore account for easy access to all your scores on MuseScore.com.