If you just want to test/preview, you can click the Android icon on the top right of the Godot editor. This will load the game onto the phone. As soon as adb devices is ready, that icon should appear. Make sure your phone is in developer mode, that the phone USB setting is set to media device or transfer files, that you've trusted your computer (it should ask you the first time), and that Unknown Sources APKs are supported.
You can also check your Godot editor settings under Android. It's possible one of the options is missing or misconfigured. Specifically you need jarsigner to be installed on your system and set to the right directory in Godot. Hope that helps.
