In order to uninstall/delete an existing App on the device you can either Uninstall from the Device it self as any other regular app. This way of uninstalling requires more steps, developers can do it faster via the ADB tool using the following command:
adb shell am start -a android.intent.action.DELETE -d package:<your app package>
Ex. If the package name of the app was com.justsikh.app, the command will look it.
adb shell am start -a android.intent.action.DELETE -d package:com.justsikh.app