All app updates are done through the app library flow. To update an app, you'll actually overwrite the current version with the new, updated version.
From Device Manager, go to the Apps and Networks.
Click next to the app that you want to update.
Change the app name to reflect a new version of the app (ex: app-name-v2) but keep the .apk name and URI the same. This lets Device Manager know that it should overwrite the current version of the app with the new version.
Click Save App.
The next time your headsets that include the app sync with Device Manager they will update to the new app version. You can force this update before the next regular sync by turning your headsets off and back on again.
Add a new app to your library by clicking Add an App in Apps and Networks.
Create an app name that clearly shows that this is the updated version of the app.
Make sure that the .apk name and URI are different. If you use the same .apk name and URI Device Manager will overwrite the existing version of the app with the new version.
When you're finished, click Review App to save the app to your Library. If you don't see the new version saved in your library, try refreshing the page.
The next time your headsets that include the app sync with Device Manager they will update to the new app version. You can force this update before the next regular sync by turning your headsets off and back on again.
Keep in mind, if you go with the second option of creating a new app in your app library for the update, the installer will replace the old app with the new one on the headsets, but you will see multiple versions of this application. To remove the older versions, the obsolete apps in Device Manager will need to be deleted from the library.