In order to update the Qminder TV app, first close the app and then go to the App Store and select the Qminder app.
On the Qminder app screen you can check if an update is available and manually update by clicking on the white update icon. If there is no update icon, the app is already up-to-date.
To update the Apple TV software, go to Settings > System > Software Updates and select "Update Software". If there's an update, select Download and Install. Wait for your Apple TV to download and install the update. Don't disconnect or unplug your Apple TV until the update completes.