Add tester to my project remotely?

I have a product in my console, and a handful of test devices that I have flashed with various versions on my code. I can upgrade them and interact with them in the product console just fine. I now have a remote user that I would like to be my first offsite tester. They have a photon that is connect to their wifi and they can interact with it via their app, but for the life of me I can’t figure out how to add their device to my product. I have tried to add their device id in the console but that only seems to work for MY devices. Anyone have a slick way to accomplish that?

One way: If they are part of your development team you can add them to your Particle development team. You will be able to move their device into your product.