This can become pretty frustrating as you do not see any X button placed on the widget itself, neither on the notification screen addon. However, removing these two things can be done very easily.
Removing WatchON widget and notificationRemoving the widget and notification addon can be done in just a few seconds and all of the options can be found inside the app's settings menu. This post may seem useless to you as these are pretty basic instructions but believe me, some people may have never thought of checking in the app's settings menu for this.
Run the WatchON app and press the menu key on your phone which should make a contextual menu popup from the bottom. Now tap on Settings.
Now you should see two settings - one for the notification in your notification screen and right below it one for the lock screen widget. Simply uncheck the option for notifications and switch off the option for the lock screen widget as shown in the screenshot above.