Once you Add your Sign to the Mango Signs dashboard, you will be able to send slides to it. If you only have one Sign added, this will automatically happen when you edit a template or save a slide.
Your Signs will show up on your dashboard as well as under the Signs tab on the right hand side of your dashboard. You can see if they are online, or offline(not able to connect to the internet), as well as how long they have been offline for.
Once you add a sign, you don't want to ever delete it unless you are not going to use the device or TV any longer. If you accidentally delete a sign, you can generate a new sign code by following these instructions.