Testing Your App on a Device
First, build your app using the browser preview until it is complete. You should not build for a device until everything is ready using the browser preview.
For Android, you can test right away with no further setup. Visit your app customizer Build and Preview tab, expand Device testing, and click Build.
For help, please see this article.
Testing on iOS devices requires an active subscription, and we must generate your certificates and install them before you can build for iOS.