If your looking to test your app on an actual device make sure to enable debugging on your phone. To do this you generally follow the following steps:
- Open the ‘Settings’ on your phone
- Open ‘About phone’
- Click multiple (about 7) times on Build number, a dialog will show up informing you that you are now a developer.
- Go back to ‘Settings’ and click on ‘Developer options’
- Enable USB debugging
You also need to allow your computer to trust your device. This you do in the dialog that pops up on your phone, after connecting with USB.